DI Lewis returns to Oxford after two years' secondment to the British Virgin Islands, where he was sent to recover from his wife's death. He is reluctantly assigned by his new boss, DCS Innocent, to the murder of an Oxford mathematics student who is shot while participating in a sleep study. The key-code used to access the sleep lab is assigned to a fellow maths student, Daniel Griffon, but Daniel's maths tutor has provided him with an alibi. Daniel is a maladjusted young man who will soon inherit his father's automotive empire. He is disruptive and has no respect for his uncle, who now heads the company. The future of the company rests however on an impending deal with Japanese investors who insist that the family unity is all important at this time. When two other murders occur, Lewis must decipher a cryptic clue left in an old case file by his former boss, Chief Inspector Morse: "Polo not king after all".

Several other references are made to Morse: on his leaving London Heathrow Airport, Lewis is nearly run over by a red Jaguar Mark 2 (which also reminds him of his wife Val’s death in a hit-and-run); he knows the word "bruxism" (tooth-grinding) as a result of spending "15 years working for a crossword fanatic"; Trudi Griffon knew Morse and says: "He was a man you could talk to"; Griffon's daughter Jessica Pollock is being examined for the "Endeavour Award" which had been endowed by an anonymous donor for music that spoke to the soul.

The plot bears some self-conscious parallels to Hamlet, and there are references to King Lear - the first victim is called Regan Peverill - and A Tale of Two Cities. The screenplay is also mathematically literate: professor Ivor Denniston dismisses his class with the joke that there's a sign reading "Heisenberg might have lived here." Lewis asks: "That Heisenberg joke – the uncertainty principle?” to get the riposte "I'm not sure." There are various abstruse clues: the griffin is a cross between an eagle and a lion; perfect numbers are those that are the sum of their factors: 6 = 1+2+3; 28 = 1+2+4+7+14; the next two are 496 and 8,128 – which turns out to be the prime suspect's computer password. Denniston was the only one who could have guessed that the key code to the sleep lab was '12 47 14'.

DI Lewis and DS Hathaway investigate the murder of Dean Greely. As the investigation continues, they discover that Greely and three other men had formed a club during their Oxford student days, the Sons of the Twice Born, which refers to Dionysus, a hero of Nietzsche:

• Harry Bundrick, who runs a bike shop with his mum
• Sefton Linn, college master and prospective vice-chancellor
• Theodor Platt, last remnant of a wealthy family, failed author and cocaine user. He uses a wheelchair since being involved in a head-on collision when drugged, causing the second driver's death (thus Platt's behaviour eliciting Lewis’s ire)
• Dean Greely, a failed painter staying in a houseboat.

Currently, the men have little contact with one another and initially deny that their club existed. The group keep their ex-membership in this disreputable club secret, although they each have a gold ring bearing the image of Dionysus. When a second member of the foursome, Linn, is murdered, it becomes apparent that they have a secret from 30 years ago, and that someone is out for revenge.

It transpires that the murders have been masterminded by two women. Tina Daniels had been a prostitute and had recommended her colleague Patsy Worth to Harry Bundrick. Patsy got drunk or drugged with the Sons of the Twice Born, and they decided to murder her in order to take out her adrenal gland and extract the adrenochrome, which was reputed (by Hunter S. Thompson) to give a very good high. It was Platt who actually carried out the murder. Patsy had a daughter, Anne, whom Tina brought up. Anne trained as a nurse and got a job nursing Platt. When Platt chokes, Anne saves his life (in Lewis’s presence) although, as Platt tells her, she could have let him die. The couple seem to be reconciled, but in reality Tina and Anne are manipulating the Sons of the Twice Born to murder each other:

• First Tina tells Linn that Greely is near death and is planning to come clean, so he must kill him if the secret is to be kept;
• She then poses as a journalist named ‘Fury’ (an allusion to the avenging Furies of classical literature) to goad Platt into shooting Linn;
• However, Harry Bundrick is to be spared as he has shown remorse.

This leaves Platt outstanding – and he is the only one who knows where Patsy is buried. Anne therefore telephones him, pretending to be being held hostage and that her abductor will release her only if he tells her where her mother's grave is. He tells her she is buried by the statue of Dionysus in their park. She then reveals the plot and sets their two Belgian Shepherd dogs on him, which tear him to shreds. Patsy’s skeleton is disinterred.

Anne had sent Lewis a cryptic note reading "His best friends killed him because of a boast", which can be interpreted as meaning that, like Actaeon, he boasted of being a better shot than Diana, and his dogs killed him. Hathaway says: "If Anne sent the riddle, she is guilty of premeditated murder. Doesn't it make her just like Platt? Lewis replies: "Not in my book." Tina and Anne thus stand to face a low penalty, if any, and to become very rich women by inheriting the Platt estate.

A further erudite classical detail is that Dean signs his paintings in Greek. Lewis and Hathaway consult Professor Margaret Gold, who immediately deciphers them as telephone numbers written in Greek numerals.

DI Lewis is less than pleased when he and DS Hathaway are assigned to protect Nicky Turnbull, a former convicted cybercriminal and "Rock and roll hacker" turned successful author. Turnbull is invited to speak at the Oxford Union. He is met by a welcoming committee composed of Caroline Morton, president of the Union; Jo Gilchrist, unscrupulous student journalist with ambitions to be a tabloid editor who intended to expose a professor's exam scam; Stephen Gilchrist, her brother, who is a serious scholar; and David Harvey, a rugby player who has had to retire because of an injury.

Turnbull had cheated two Oxford colleges in his computer scam and had received death threats. Lewis and Hathaway are tasked with babysitting him. Although Turnbull is everything Lewis dislikes - a criminal and a professional Geordie - he grits his teeth and does the job.

Turnbull gives his lecture and afterwards treats his audience to champagne in his hotel, which is housed in the converted prison in Oxford Castle. On the way there he is nearly run over by a jeep. Things take a more serious turn the following morning when Jo is found strangled in the hotel room next to Turnbull’s, which had been booked in Lewis’s name. Caroline emerges, having spent the night with Turnbull. She admits that after the speech, she and Jo planned a "honey trap" that would give Jo a juicy story for the press.

The next morning, after Turnbull is fatally shot by a sniper while talking to Lewis in the hotel courtyard. Turnbull’s wife Diane, who is also his agent, comes to identify his body. By an amazing coincidence, she was at school with Lewis, and he was indeed her first boyfriend. By another coincidence, David Harvey was at the same public school as Hathaway, and remembers him as the head boy. He tells him is nickname was ‘WC’, short for ‘Wolfgang Christ’, as they couldn’t work out whether he wanted to be Mozart or Jesus. It is revealed that Hathaway plays the guitar, specifically world music mixed with jazz, rock and medieval madrigals.

It transpires that during his hacking exploits Turnbull stole large amounts of money from two Oxford colleges, and that as a result David Harvey’s father lost his job and committed suicide. David gave Jo a pistol for her 21st birthday, and on the night of Turnbull’s speech brought bullets for it, hoping she might shoot him. But she refused as she found him “kind of cute”. David therefore shot Turnbull with a rifle, out of revenge.

In Summertown an Oxford housewife is found hanged in her home. The locum pathologist states it is a suicide but Lewis realises it was a staged murder, which sets him at odds with his boss, Innocent. Lewis and Hathaway learn through an unusual source, that of terminally ill Oxford college don wanting an unusual favour, that while on holiday in Madagascar the victim and her closest friend swapped husbands. What from that past was worth killing for? Josette Simon guest stars in this episode.

The murders of Reg Chapman, a maintenance worker at the Bodleian Library and gambling addict, and Nell Buckley, a popular art student, seem unrelated. However, the police learn that Chapman stole historic books from the library so that Nell and another student Philip, a brilliant, autistic young painter, could use blank pages to innocently forge letters by the poet Shelley for the international collectors' market. When both victims, for different reasons, threatened to expose the mastermind behind the scam, they were killed.

Whilst investigating the murder of R.G. Cole, an elderly gay lecturer who was found strangled at a friend's house, Lewis finds links to bare-knuckle fighting, Wagnerian opera, East Berlin, the former East German Stasi state security service and Lewis' old mentor Morse.

A student called Will McEwan shoots himself in the head in St. Mark's church, after pointing the pistol at Reverend Francis King, who is found tortured and murdered by a hot poker thrust into his head the next day. The link between both is The Garden, a pious society offering "Christian answers to youngsters' contemporary questions", and its emblem, a phoenix, to which both Will's suicide note 'On the road from Gethsemane to Calvary, I lost my way.' and a message on King's door 'Life born of fire' refer. Lewis's partner, DS James Hathaway, was a friend and classmate of Will's at both school and Cambridge. Will's father Henry McEwan apparently repudiates Will upon discovering his son's homosexuality after his death. Will's mother believed he was going steady with a nice girl. Lewis keeps searching through these circles, discovering more secrets and deceit. More blood is to be spilled, and the meanings of names proves crucial.

Following a squash injury, Robbie ends up in casualty where he meets the Donnelly family, whose school-girl daughter Beatrice had been drugged and then woke up in a field, discovering that she had been raped. Evidence points to Oswald Cooper, who worked at her school and whose prescription drug matches the doping agent. However he has an alibi, a dinner party he hosted for three former student friends, now all eminent men: Gavin Matthews, a controversial radio personality; Danny Adebayou, a city developer; and Simon Ashton, a British diplomat. The next day Cooper is found garrotted and castrated. Forensic evidence backs the view that he raped Beatrice, and his alibi is proved to be false. A friend of Cooper's who is blackmailing the three guests is also garroted. It is clear that Cooper serviced his former friends by organizing scams and deceptions for them. However, the solution to the case reveals that Cooper's murderer is protecting and preserving a far more personal secret. Jason Watkins and Kwame Kwei-Armah also appear.

Lewis and Hathaway discover that the bizarre murder of a Czech (actually, Bosnian) barmaid with an antique Persian mirror parallels a similar killing found in a newly published fantasy novel, by the young Oxford author Dorian Crane (Tom Mison). The life of another young woman is threatened, leading Lewis to suspect that the murdered girl is a victim of mistaken identity. The investigation becomes even more complex when Crane is murdered with a sword at a university function. Part of Series 2 in the U.S. Art Malik, James Fox, and Olly Alexander also appear.

A preview performance of a student production of The Merchant of Venice is cut short when the actor playing Shylock is stabbed to death with a prop knife. Lewis and Hathaway are working their way through a lengthy list of suspects when an ambitious journalist and friend of the cast (Shereen Martineau) is also killed. It turns out that a female professor (Maureen Beattie), whose ornate turreted house is a residence for her student actors, committed the murders to protect her career. Her reputation was threatened because she has connived in plagiarism by awarding a doctorate to the play’s director (Daisy Lewis) for a thesis that was actually written by the student's then-boyfriend (Bryan Dick). The student doesn’t care about the plagiarism because her only ambition is to work in the theatre, and the ex-boyfriend, who dropped out of Oxford, doesn’t care because he is a northern working-class lad with a chip on his shoulder who despises academia. Both murder victims were aware of the plagiarism. In parallel, a man incompetently running a hotel fraud (Ronan Vibert) in which his sister and accomplice repeatedly "steals" his suitcases from hotels turns out to be the hit-and-run driver who killed Lewis' wife Val. Lewis and Hathaway attend the driver's trial at which he pleads guilty to manslaughter. Part of Series 2 in the U.S. Gwilym Lee guest stars in this episode.

Lewis and Hathaway investigate the murder of a man found beaten and drowned in his bath. The deceased is identified as a religious fanatic who once attempted to murder a celebrated atheist, Tom Rattenbury (Julian Wadham), but instead disabled Rattenbury's daughter. Investigations reveal that the deceased is another man entirely, the two having chosen to swap identities. Part of Series 2 in the U.S.

Lewis, called out to deal with a noise complaint, is shocked to meet a rock star, the lead singer of iconic band Midnight Addiction (David Hayman, Anthony Higgins, Trevor Byfield), Esme Ford (Joanna Lumley), whom he had once admired, and who was believed to have drowned years ago. The body of a teenage boy, who has been repeatedly run over by a vehicle, points to a connection with members of the band. Also appearing are Simon Callow, Harry Lloyd, Daniel Kaluuya and Perdita Weeks.

With Hathaway still reeling from a particularly horrific investigation, the team investigates a murder discovered on a tour bus where none of the passengers can remember the victim. The investigation leads Lewis and Hathaway to an estate, Crevecoeur Hall, reputedly associate with treasure from the English Civil War and the ancestral home of the wealthy Mortmaignes where Hathaway grew up. The detectives are soon investigating a second murder. Part of Series 3 in the U.S.

Lewis and Hathaway investigate the killing in suspicious circumstances of Professor Andrew Crompton, amateur astronomer and Master of Gresham College. Crompton was found dead at the university observatory after making a strange confession to a priest. His widow suspected that he had been having an affair, but Lewis and Hathaway discover that the dead man had a curious obsession. Part of Series 3 in the U.S.

The body of a philandering primary school teacher is found floating in a fountain during a quiz weekend, an event which is hosted at Chaucer College over a bank holiday. Suspicion initially falls on two competitors with whom the dead man had been flirting, but then one of them dies in a similar way. Lewis soon finds that the first victim was involved in a secret government operation, and that several of the other quiz participants are connected to it too. Part of Series 3 in the U.S. Also appearing are Sally Bretton, Alan Davies and Timothy West.

Stem cell researcher Ligeia Willard is murdered with a stake through her heart on Halloween; Dr Laura Hobson reveals that the victim is a former university friend of hers. More murders occur that are connected to Laura's past, and Lewis wonders whether the pathologist is holding something back. A medium, who claims to have foreseen the death, conducts a séance, but Lewis and Hathaway rely on more conventional methods to solve the murder. Part of Series 3 in the U.S.

A reunion at an all-female college ends in a murder. Professor Diana Ellerby is leaving Oxford's last surviving all-women's college. During a reunion with old students, one of them, Poppy Toynton, is murdered. Lewis and Hathaway's investigation leads them to a connected 10-year-old attack on the sister of one of the other old students during a party at the college. In that incident, the sister was attacked and is in a coma. That case has haunted Lewis and, during the investigation, he reaches out to his former DS, Ali McLennan for assistance. As the current murder investigation continues, secrets, blackmail and more bodies are uncovered. Part of Series 4 in the U.S.

A bishop visiting St Gerard's College is found dead after drinking poisoned wine; Lewis and Hathaway suspect that she has been killed because of her progressive views. When another two killings occur, both mirroring macabre murders from a Jacobean revenge tragedy, it appears the murderer is targeting candidates for the post of vice-regent of the college. However, after learning that one of the suspects harbors a dark secret, Lewis and Hathaway realise the motive is much more twisted and that the murderer is avenging perceived slights from more than twenty years earlier. Part of Series 4 in the U.S.

A student dies during a residential clinical trial for a new antidepressant. An investigation by Lewis and Hathaway is hampered by the professor of psychiatry who was conducting the trial, but the pair eventually establish that the participants in the trial are acting under the malign influence of the drug. Part of Series 4 in the U.S. This episode features guest actors from rival ITV crime drama Midsomer Murders: Christina Cole, Sam Hazeldine and Lucy Liemann.

Lewis and Hathaway investigate the murder of a businesswoman who had apparently been blackmailing the father of her protégé. The memoirs of a former head of MI5 provide Lewis with a vital clue, one which furthers the investigation's ties with old romantic passions and the Irish Republican Army (IRA). Part of Series 4 in the U.S.

A botanist accidentally unearths the recently buried corpse of a professor who was fixated upon solving "The Hunting of the Snark", a cryptic nonsense poem by Lewis Carroll. The victim had a long-standing rivalry with his brother, giving Lewis and Hathaway an obvious suspect, but the case is hindered by the mind games of two students who seem intent on causing trouble in their quest to gain admittance to a mysterious elite club. Part of Series 5 in the U.S.

A professor feels humiliated when her internet dating video is leaked onto a website and watched by her students. The next morning she is found dead, the victim of what appears to be a straightforward suicide. However, Lewis is not convinced and digs deeper, identifying several suspects, including the site's founder. But as he and Hathaway get closer to the truth amid a rising death toll, they find their personal and professional lives dredged up online for all to see. Part of Series 5 in the U.S.

The murder of a babysitter throws up a number of questions for Lewis and Hathaway. Was she the intended target, or was the killer aiming for her employers? Was the crime calculated or opportunistic? And why was she elaborately tied up after being murdered? Soon after the first death, a friend of the dead woman is brutally killed, which brings up a number of new questions. As the detectives dig for clues, they are led into a world of suburban swinging and fetish photography, far removed from the Oxford they know. Part of Series 5 in the U.S.

When a visiting American academic delivers a controversial speech about "criminal dangerousness", many audience members are worried that his ideas could be used to target ethnic minorities. Thus when he is found hanged the next morning and Dr Hobson quickly discounts suicide, Lewis and Hathaway realise they have many suspects – from the local anti-racism activist who is first in voicing her disgust at the professor's beliefs to the women who had bombarded him with threatening emails. But then another body turns up, and the detectives find themselves pursuing even more leads. Part of Series 5 in the U.S.

The death of psychologist Reuben Beatty throws up a number of questions when he is found murdered in the offices of psychic Randolph James. It soon becomes clear that the two were one and the same: Beatty is moonlighting as a clairvoyant. Lewis struggles to unravel his baffling double life whilst contending with Oxford's sinister psychic community. Part of Series 6 in the U.S. Shown in one piece on 16 June 2013.

Chief Superintendent Jack Cornish, an ex-colleague of Robbie's, goes missing and a recently embalmed body is discovered near an isolated farm track. Lewis takes the awkward, young but bright DC Gray (Babou Ceesay) under his wing to investigate the case. It transpires that Cornish has gone to ground in a cottage in Croatia, where he manufactures crystal meth, which is smuggled into Britain inside corpses being repatriated to undertaker Brian Miller. Hathaway is conveniently on holiday in nearby Kosovo that week, helping to renovate an orphanage. Lewis relishes asking him to pop over to Split to dig him out, leading to the dialogue: "What’s the time difference?" – "About a century. You know Split is in a different country?" – "Only recently."

Peter Faulkner, with whom Lewis had previously had a run-in, had murdered the other members of the gang Johnny Jay (because he objected to his son Liam being involved) and Dr. Matt Whitby, and tried to murder Liam’s girlfriend Ruth Wilson in case Liam had told her anything. Cornish walks free as there is no proof of his guilt. On the way out of the police station he asks Lewis: "A drink for old time’s sake?" "There isn’t a spoon long enough."

The episode is interspersed with incidents in the culmination of Lewis and Hobson’s love affair: a longing look, her hands on his shoulders, holding hands and finally a passionate kiss in front of Innocent and Hathaway. Lewis has finally got over his wife’s death: at midpoint Hobson asks how Lewis is, and he says “Val is slipping away. I’m turning over the page.” She replies “Right!”

Part of Series 6 in the U.S. Shown in one piece on 23 June 2013.

After seven years of ducking the question, Lewis and Hobson are embarking on a relationship, though the detective has a new puzzle to solve. An elderly former don, Richard Seager, is run down by his own car on the night of his release from prison, where he'd been incarcerated for killing a young woman while driving drunk. Before dying, he mysteriously scratches what looks like the number "500" into the paintwork. Lewis must contend with Seager's wife, convinced that the sister of her husband's victim is the guilty party. Part of Series 6 in the U.S. Shown in one piece on 30 June 2013.

Hathaway returns from making the Camino de Santiago pilgrimage, and he starts work on his first murder case as an inspector with the help of a new partner, DS Lizzie Maddox. As the pair delve into the worlds of neurosurgery, blood sport and animal rights, Hathaway struggles to solve the case. Unwilling to delegate responsibility to an increasingly frustrated Maddox, he is overwhelmed by the work involved, and requests help from Innocent, who persuades the now-retired Lewis to come back on a one-year contract (to the annoyance of Laura Hobson, who had hoped for a quieter life with her retired partner). A well-respected neurosurgeon has been shot, and the case becomes still more complicated when his friend and business partner, the co-owner of the hunting estate where the shooting occurred, is also murdered -- apparently with the same weapon, though it was locked away in the police evidence room after the first murder. This second murder victim had been the prime suspect for the first killing, but there's no shortage of other suspects, as the neurosurgeon turns out to have made several enemies through his work, including a complaint of malpractice for a botched operation.

Part of Series 7 in the U.S. Shown in one piece on 5 October 2014.^[24]

Lewis, Hathaway and Maddox's abilities as a team are severely tested when they investigate the brutal stabbing of American classics scholar Rose Anderson. The bizarre case that follows takes in the cocaine trade, astrophysics and ancient drama.

Anderson was killed while jogging. She had been having an affair with Felix Garwood (whose wife Philippa was her academic supervisor), an astronomy professor, but Garwood had recently dumped her. She retaliated by knocking him off his bike in her blue Mini. Garwood later meets a violent end in his office filled with antique astronomical instruments, including a telescope that had previously belonged to Isaac Newton.

Meanwhile, questions arise regarding the classics professor Simon Flaxmore, who had made his name by apparently rediscovering the lost Euripides play Alcmaeon in Corinth (Ἀλκμαίων ὁ διὰ Κορίνθου, 405 BC). He is insistent that he hardly knew Rose at all and had never spoken to her, but this is considered unlikely, given that she was studying the subject on which he is the world expert. Hathaway works out that the "rediscovered" play is a fraud, as it refers to the "two lions of Nemea", whereas the constellation of Leo Minor was only so named by Johannes Hevelius in 1687. Flaxmore’s fingerprints reveal that he is Linus Cage, who was imprisoned for fraud and released in 1985. He was appointed an Oxford classics professor in 1992 on the basis of a fabricated CV. Anderson had discovered this and was planning to expose him.

Felix's wife Philippa’s sister, Jennie Brightway, has a daughter Tabitha with Fanconi anaemia, whom Anderson tutored. Jennie Brightway and her husband Paul, desperate to engender a saviour sibling via in vitro fertilisation, have been struggling to find the money for this expensive procedure, but Anderson had donated a large sum to help them. Could they be connected somehow to the murders of their tutor and brother-in-law? Chemical analysis shows that the telescope used to beat Garwood to death had been wiped clean with lens wipes, which points to Paul Brightway, who is an optometrist. It was only when they undertook in vitro fertilisation that Paul Brightway discovered that Jenny Brightway and Garwood had had an affair and that Tabitha is Garwood’s biological daughter. Paul Brightway killed Garwood because he threatened to take Jennie Brightway and the children away from him.

Part of Series 7 in the U.S. Shown in one piece on 12 October 2014.^[24]

Thirteen years ago, Lewis successfully apprehended hammer killer Graham Lawrie, who was convicted and sent to prison. Now Lawrie is on the verge of regaining his freedom thanks to new evidence. Lewis fears the worst, but nothing can prepare him for a string of murders resembling those in the original case. With his mentor's reputation in jeopardy, Hathaway races to catch the killer. Part of Series 7 in the U.S. Shown in one piece on 19 October 2014.^[24]

A new boss arrives at Oxfordshire Police, and he begins to question Lewis’ role as a consultant. After an exhibition of anthropomorphic taxidermy, the body of a young avant-garde artist is found. Lewis, Hathaway and Maddox must delve into the worlds of social media, drugs, taxidermy, alternative art and the homeless East European community. Meanwhile, Hathaway confronts his father and sister, with whom he does not have good relationships. Part of Series 8 in the U.S. Shown in one piece on 7 August 2016.

Lewis and Hathaway are called to investigate a body in a woodland. Realising three more murders may follow, the team must hurry to catch the killer. Hathaway is struggling to cope with his father’s illness, as he begins his search to understand his father's activities before dementia set in.

Three people are murdered, all members of a spiritual cult, the "Companions of Coinherence". This group revived the ideas of Charles Williams, a member of the Inklings, an Oxford literary discussion group that also included J. R. R. Tolkien and C. S. Lewis. Williams taught that it is not only God that can forgive; we can also take another’s guilt on ourselves through the ritual of "substitution". The members of the cult bear a tattoo in the form of a triskelion as used in Gothic tracery.

The murders follow the four stages of the alchemical process of the magnum opus:

1. Negredo – black – raven – decomposition: College dean and Tolkien specialist Phil Beskin is lured into the woods on Boars Hill, knocked out, semi-buried and covered with maggots.
2. Albedo – white – moon, purification: After undergoing the substitution ritual, Annapurna Kinneson is strangled and then tied to a post in the river so that the water can purify her
3. Citrinitas – yellow – sun, male, enlightenment: After his assistant Gina Doran is lured out of his tattoo parlour, Jay Fennell is killed and covered in a yellow substance
4. Rubedo – red – blood

Carina Beskin, Phil Beskin’s sister, confesses that eight years ago the four – Phil and Carina Beskin, Fennell, and Kinneson – were larking about, driving home late at night without headlights, and killed Francis Fisher, a practising alchemist. Carina Beskin was driving while drunk, but the group escaped punishment because they lied. Phil Beskin and Kinneson had used the doctrine of substitution as a way of coping with their guilt.

Lewis and Hathaway realize that student Sam Langton, who is in a relationship with Carina Beskin, is in reality Francis Fisher’s younger son John, who is wreaking vengeance. They track him down to a farmhouse near Burford, led there by traces of the local limestone from his shoes. They interrupt him in the process of concocting a red liquid and overpower him before he can drink it. Under Hathaway’s persuasion he tells Carina Beskin, who is dressed in red, that he forgives her. She asks what for, and he says “for murdering my father”. Suddenly she realises who he really is and berates him for killing her brother and her friends.

Three ongoing plot lines also develop: (1) Laura is persuading Lewis to look forward to their trip to New Zealand; (2) Moody overcomes his doubts and agrees that Hathaway will get on fine while Lewis is away; (3) Hathaway visits his old monastery school after 17 years’ absence, and learns from Father Placid that Hathaway's father had been talking to him about how to repair the damage caused by the father's being so distant from his son. Though he had previously angered his sister Nell by leaving all the filial duties to her, Hathaway rings up his dad and asks if he can visit him.

Part of Series 8 in the U.S. Shown in one piece on 14 August 2016.

Last ever episode. A summer’s day in Oxford is torn apart, when a parcel bomb explodes, and the team are called in to investigate. The victim is a womanizer who was known to have had numerous affairs with younger women. With his six-month trip to New Zealand with Hobson on the horizon, Lewis is in a race against time to save his career and relationship. In the end, Lewis and Hobson finally leave for New Zealand. Part of Series 8 in the U.S. Shown in one piece on 21 August 2016.