Three days before her wedding, Luella Shakespeare hires private detective Frank Hathaway to investigate her fiancé, Clive Brenton, whom she believes is having an affair with his secretary, Janice Bardolph. She calls him off the case when she realises that she was mistaken. Frank had not found evidence of an affair, but found out that Clive is using different identities on dating websites. Frank interrupts the wedding, but Luella has the security guards send him away. Shortly after the wedding at a hotel, Clive is stabbed to death with Luella's hairdresser's scissors. Luella is arrested by the police, who release her soon after. She discovers that her savings have been stolen from her bank account.

Hathaway and Shakespeare find out that Clive was a bigamist with an accomplice, Janice – who stole Luella's £250,000 that Luella had invested in Clive's company. Luella stops the accomplice from leaving with the money and retrieves it from her. Frank thinks that Janice is the killer, but the police state that Janice could not have killed Clive, although they arrest her for her involvement in Clive's bogus business. The investigation returns to the hotel and one of Clive's previous wives, Veronica Vinten – who admits that she killed Clive after finding out that he had faked his death and was marrying Luella. The police arrest Veronica. Frank, deep in debt, reluctantly accepts Luella as his partner in his detective agency.

Guest star: Nigel Whitmey (Nigel Whitney in credits).

Frank and Luella are employed by Penelope Pincott to investigate sabotage at the business she and her husband Owain run, Shady Nooks care home. Sebastien goes undercover as a care assistant. During lunch, when all the staff and residents are in the dining room, Penelope falls to her death from the roof. Suspecting one of the staff or residents of the murder, Frank and Luella have to work out how it was done. Sebastian discovers that the saboteur is a resident, Johnny Falstaff. He does not like living there and was deliberately causing various problems in an attempt to have his son 'rescue' him from the home. Care worker Soozie is also a murder suspect when the investigation reveals that she is attracted to Owain. Frank works out how Penelope's (already dead) body crashed to the ground from the roof when all the home's residents and staff were present in the dining room. The death of a resident exactly a year ago provides a clue – the late resident's son Ian blames Penelope for the death. At the end, it is revealed that he became the home's cook six months later and killed Penelope in revenge on the anniversary of his mother's death.

Guest star: Timothy West

Frank and Luella are employed by a funeral director, Peter Quintus, after he is visited by "Mr R" and "Mr G" who say that a criminal organisation has hired them to kill him in 24 hours time. He is told not to involve the police or there will be consequences for his family, and there are two attacks on his wife, Anne. After one of the attacks, Frank finds a photograph relating to an art college that Anne attends. Luella interviews the neighbourhood warden, Melvin Pipkin, who is fond of Anne, and who is later found dead following a hit and run. Sebastian interviews Peter's man-eating ex-wife, who had been cheated out of money in her divorce settlement. It is discovered that Peter was violent towards both his wives and that Anne has persuaded two teachers at her college to pretend to be Mr R and Mr G to scare him. Melvin was killed by Peter, and the police arrest him. Anne leaves with Mr R, with whom she is in a relationship.

Frank and Luella are employed by magician Lawrence Pross and his daughter Maggie after his iron maiden trick kills a woman, wealthy Jill Shiplake, on stage. The Prosses believe rival magician Anton Dukes is responsible. The victim was bickering with her husband that night and with the theatre usher. Frank realizes the victim might not have been selected at random and suspects the husband, Stefan. They find evidence of Stefan's guilt but then realize Stefan and his wife had swapped theatre seats.

The mayor of Arden is found murdered with a blunt object after firing a shotgun, and Detective Inspector Marlowe's prime suspect is burglar William 'Billy the Brick' Porter, a former informant of Frank's. Billy turns up at the S&H office, begging Frank, who is indebted to him, and Luella to prove his innocence. Their investigations lead to the press reporter who found the body, the deputy mayor, a property developer of ancient woods, and protesters against the development. Sebastian discovers Billy has a blood-stained T-shirt.

Frank and Luella are employed by narcissistic former hospital soap star Sally Balthasar. Sally has received a death threat after planning her comeback by rewriting Shakespeare's play Romeo and Juliet and playing the female lead. She calls her version Juliet and Romeo, and her character does not die. Her changes to a classic play offend cast members, the director, the backstage crew, and Shakespeare fans. Things come to a head when Sally is poisoned and unable to continue. The director then reverts to Shakespeare's original play. Frank and Luella watch old episodes of Sally's soap opera and find a link between past and present.

Frank and Luella are employed by gift shop owners Diana and Leon to investigate an ex-employee, Lola, who is claiming compensation for a workplace injury. The investigation is hampered by Martin Mariner claiming to be Frank's uncle. Frank finds Diana dead in the gift shop, the victim of a robbery. Suspicion falls on Leon and then on Mariner, who had money covered in Diana's blood, and he incriminates Lola's boyfriend Phil, a name linked to Diana's phone. Sebastian goes undercover as a transvestite at a bar and as a gas man at Lola's house.

Frank and Luella are employed by troubled 18-year-old Hamish after he has premonitions of murder. They join him at a spiritual retreat run by his mother and stepfather. Staying at the retreat are his ex-girlfriend Lily, his best friend Uzoma, and others. Lily's psychoanalyst mother, Polly, had been counselling Hamish and Uzoma at their sixth-form college until she was sacked. She tries to remove her daughter but she refuses to leave. The next day Polly, whose relationship with Uzoma was posted on social media by him, is found dead with Hamish. He remembers nothing and is arrested by Marlowe. Sebastian goes undercover at the teenagers' college. It is discovered that Hamish was adopted after his mother was murdered by his father when he was four, and Hamish found her dead. The 'premonitions' were his vague memories. His father was using a false identity and married Hamish's mother. He also murdered Polly to prevent his real identity being discovered; he is arrested by the police.

Frank and Luella are employed by owner/chef Len Tekler of top restaurant Hiverna after sabotage in the kitchen. Frank suspects an inside job, but Tekler suspects food critic Paulina Stainton. Sebastian goes undercover in the kitchen. The restaurant is closed when customers suffer a food poisoning incident. Tekler is murdered by poisoning, and Frank and Luella investigate the relationships of Paula Stainton, Tekler's wife Cecillia, his son Milo, waitress Dita Pardy, and restaurant ex-partner Trevor Cordiss; and the death of Tekler's brother, Michael, who hanged himself 20 years earlier - all seemingly connected.

Frank and Luella are employed by Lady Tania Bede when a valuable necklace and her 18-year-old daughter, Mia, go missing. She offers them £10,000 to recover the necklace by that evening. A ransom demand of £50,000 for Mia is made. The investigation reveals Mia's relationship with a man other than her boyfriend whom she met in the gardens of her home. They find evidence of garden labourer Lee Sandridge fencing the necklace that turns out to be a fake. Head gardener Ron Greenvale, having already tendered his resignation, denies he is having an affair with Mia, who is less than half his age. A payment of £200 Mia made to a local private hospital adds to the mystery. Frank and Luella, with Sebastian undercover, attend Lady Bede's ball that evening to solve the mystery.

Frank and Luella are employed to find a valuable mongrel dog that has gone missing. The dog, heir to a £320 million fortune since his owner died, lives a pampered lifestyle with numerous staff; the staff are dependent on the dog, as on its death the estate goes to charity. A £200,000 ransom is demanded and Frank and Luella suspect an inside job. The ransom drop goes wrong and the dog, identified by the dog's vet, who had despaired at the dog's pampered lifestyle, is found dead.

Frank and Luella are employed by Adrian Messenger, the writer/manager of a fantasy historical reenactment group, to follow his wife, whom he suspects is having an affair with another member, Major Tony Suffolk. Posing as members of the group, they are present when two members, Suffolk and another, are hit by crossbow bolts, Messenger's wife is arrested and Frank and Luella are asked by her husband to prove her innocence. They uncover that Suffolk had broken off the affair with Messenger's wife and that his army record is not what it seems.

Frank and Luella are employed by Anastasia Kusk to find her husband, Pavel. Tracing him to a hotel, Sebastian finds him dead and minus his right hand. Anastasia asks Frank and Luella to continue on the case, as her husband had a valuable art collection, but all are not who they seem, and two criminals are also after the hand, which has come into the possession of an out-of-work actor whom Sebastian has met to his cost. Events take an odder course when the left hand is cut from the corpse in the mortuary.

Frank and Luella are employed by Julienne Fortby after she is injured during the psychic TV show she co-hosts with her sister, Marcia. She believes her sister is involved, until Marcia is also injured. Frank believes it is all fake, but Sebastian falls under Marcia's spell while Frank and Luella investigate a hostile audience member whose husband had died from a stroke and whose son works on the show.

Frank and Luella are employed by Portia Montgomery, a solicitor, to find evidence that her client is innocent of a violent assault during a quad bike theft, at a poultry farm, that he was part of. Frank and Luella search for a potential witness, a homeless woman sleeping rough at the farm at the time of the theft. The witness turns out to be Portia's estranged mother and her client's girlfriend turns against him and a poultry distributor begins making threats.

Frank and Luella find themselves victims of lookalike imposters and are arrested by Marlowe and Keeler after £30,000 is stolen from an elderly lady. Out on bail, they discover the imposters are out of work actors employed by someone who has hacked their computers. Using Sebastien's acting skills and computer nerd Spider, they lay a trap that backfires leaving Frank to look for someone looking for revenge.

Frank and Luella are employed by Ava Foyle to find her missing husband, Lorenzo, who has many debts especially to the casino where Ava works owned by two sisters, Rose and Queenie. Frank and Luella investigate the casino and discover Lorenzo had affairs with one sister, Queenie, and a casino player, Lady Chaucer. Luella finds she has a talent for Poker and wins a memory stick from a thief. Frank finds himself in a deadly game of roulette with Rose that will cost him his life if he loses the spin of the wheel.

Frank and Luella are on surveillance when a man suffering from amnesia stumbles across their car. The man has no identification; only an expensive watch and a locker key. With Gloria's help, they get a clue that takes them to the Duke Vincent hotel where they discover evidence that he stayed there as a guest and worked as the hotel gardener but the staff deny all knowledge of him. As more of the man's memory returns, it is apparent that he had propositioned the young receptionist whose mother is the manager of the hotel.

Frank and Luella are employed by Frederick Greenwood, owner of exclusive tennis club Runningbrook, who has received a death threat. Luella's mother, Genevieve, is the club's social secretary and romantically linked with Greenwood. The death threat turns to a blackmail demand after the head tennis player, romantically linked with Greenwood's grand-daughter, is poisoned with Aconite. Greenwood has to borrow the blackmail demand from Luella's mother, arousing Luella's suspicions that the poisoning and blackmail are linked.

Frank and Luella are employed by Bianca and Anthony Percy, a young couple who had their furniture stolen by a bogus removal company. Tracking down the conmen to their lock-up, they discover one of them shot dead and the other (Billy Porter) later in their office. All the furniture is recovered except for a statue of an angel containing the ashes of Bianca's grandmother, mother of underworld crime boss Claude Mortimer. Mortimer captures Frank, Porter, and sergeant Keeler and puts them in a container destined to be lost at sea. Together, Luella and Inspector Marlowe search for their respective partners and past secrets are revealed.

Frank and Luella are employed by Henrietta Bolingbroke to close down an old bingo hall she wishes to redevelop. Frank is upset to find an old nemesis, Eddie Monmouth, he imprisoned eight years previously for violent crimes working at the hall. He claims he is a reformed character alone since his wife left him and an estranged daughter he cannot find. When the owner Lucky Green is found dead, Frank suspects Monmouth who unexpectedly confesses to the murder. When they find the murder weapon at the home of an elderly bingo player, their attention turns to JJ (the bingo caller), Megan Poins (the assistant manager), and a missing contract signing over the hall to Bolingbroke.

Guest star: Vic Reeves (credited as Jim Moir)

Frank and Luella are employed by Tony King, lead singer of the heavy metal rock band, Caliban's Claw. King, intent on making a comeback, believes the Devil is trying to kill him. Years before, the band had made a pact with the Devil for success which they had until a fateful coach crash killed one of the band, Ricky Cornwall, who was the fiancé of Gloria Fonteyn. The band fell apart and disbanded; a second member, Bushy, dies a few years later. The third member dies in front of Frank and Luella, fleeing from the Devil, leaving King the only member alive. Frank and Luella delve back to the fateful crash and the survivors which included Gloria and Bushy's baby son.

Frank and Luella are employed by the mother of Haroon Malik and his friend Poonam. Raja was killed, crushed by fallen carpets, in a carpet warehouse owned by Poonam's father from whom she has been estranged, leaving her two sisters, Parthi and Pia Raja, to run the business due to his dementia. Frank and Luella uncover a failing business closing its stores and selling carpets to a rival business, confirmed by undercover work by Sebastian and Poonam. Frank and Luella find a notebook with a verse addressed to one of the three sisters as P that makes them think the death was a crime of passion.

Frank and Luella are employed by Sir Tim Forbes-Allen to find the missing curator, Lucian Shaw, of his new Shakespeare museum, fearing he had been kidnapped. The museum had been beset by female protestors, The Herstorians, angry at Forbes-Allen's policy towards women in history. Frank and Luella find Shaw tied up in the basement when they receive news that Forbes-Allen has been murdered. Shaw employs them to find a love letter from the victim and a note from the letter holder and a cheque, in payment for finding Shaw, from Lady Forbes-Allen provides a link to the murderer.

Guest star: Simon Williams

Frank and Luella are employed by self-obsessed Odette Dixon to investigate a fire at her hair salon that left her employee, Joelle, in a fatal coma. She suspects her rival salon owner Isobel Harris, whom she accuses of previous attempts to damage her business. Luella knows both Dixon and Harris from the time she owned her own salon and takes Frank and Sebastian into the cutthroat world of hairdressing. Together they uncover the tangled relationships that enabled Joelle to blackmail staff at both salons.

Frank and Luella are employed by Gordon Minola to investigate threats against him and his company Minola Energy by green activists known as Mortal Coil led by Curtis Price. Minola's daughter, Kate, is a member of Mortal Coils and her father is keeping her a virtual prisoner at home because his other daughter, Bianca, will marry the wealthy Lucas De Boulay. Leaving the wedding, Bianca and Lucas are kidnapped and Minola receives a ransom demand for £2 million. Somehow Bianca escapes, claiming Curtis murdered her husband by stabbing and Keeler arrests Curtis after finding his fingerprints on the murder weapon. Kate pleads with Frank and Luella to prove Curtis is innocent.

Frank and Luella are employed by Emilia Belmont to investigate her mother Leah's death when Emelia was a child, in a car accident for which she holds her estranged father responsible. Her father is part of a group of uncooperative cryptic crossword compilers who had been searching unsuccessfully over the years for a fortune using cryptic postcard clues left by Leah who despised the group. When Emilia's father is found dead in a park by a memorial bench to Leah, Emilia calls a halt to the investigation. Frank and Luella carry on and solve the clues leading to a pawn shop and Emilia is confronted by an uncomfortable truth from the past and present.

Frank and Luella are employed by Melanie Montague, lessee of The Barchester Arms, to find a stolen photograph of Old Lil who is purported to haunt the pub since she was murdered 120 years ago. The investigation is hampered by ghost hunter Penelope Lawrence trying to prove the ghost's existence. Time is of the essence as the pub's lease, renewed every thirty years, is up for renewal or the pub reverts to the Capulet family (something family head Stephen Capulet is keen to see happen). Frank and Luella discover a diary revealing the photograph contains proof of pub ownership. Lawrence is murdered as she leaves an answerphone message to Frank and Luella admitting she had stolen the photograph.

Guest star: Rosie Jones

Frank and Luella are employed by Jessica Duke to check her son, Charlie, is not in any trouble and gives them access to her computer that has tracking software to her son's phone. Charlie, like his sister Isabella, is expected to go to Oxford University after taking specialist teaching at the Syracusetution Centre. Frank and Luella suspect an affair between Charlie and one of the tutors, Cassie Dorcas. Dorcas is later found murdered and the case takes a new turn towards fraud, leaked examination papers, the centre's top tutor Amit Aziz (whom Dorcas disliked), and how far the Duke family would go to protect each other. Sebastian realises his dream to appear on stage at Stratford.

Guest star: Tamzin Outhwaite

Frank and Luella are employed by Bertie Tark, CEO of high tech company Forosa, to find a mole leaking secrets of a new fashion app about to be launched. Their old computer geek friend Spider, who acts as head of security, recommended Frank and Luella and together they investigate the employees who present a happy front despite the head of development, Dean Parolles, being an overbearing taskmaster. When Parolles is murdered, suspicion falls on employee Helena Mau, who claims to have invented the original app, but Spider (who has fallen for her) is convinced she is innocent.

Frank and Luella are employed by Beatie Delamar to investigate a curse on her Dance School, causing the accidental deaths of three directors. Sebastian goes undercover and discovers rivalry and jealousy at the school, as well as the fact the school is owned by the six directors in a Tontine now consisting of Beatie Delamar, her head teacher Tania Phikes, and Ben Lovedon, Delamar's dance partner, who had disappeared years ago. When Phikes is murdered, Frank and Luella find Lovedon together with the murder weapon in his living room. Delamar cannot believe her first love committed the murders and a unique hybrid rose, grown by Lovedon, named after Delamar leads Frank and Luella to a murderer closer to home.

Guest star: Danny John-Jules

Frank and Luella are employed by Jonathan Skylark to investigate the death of his wife Ophelia at a river party, promoting their failing business and her 40th birthday, by drowning in the River Avon. After an open verdict by the coroner, a £500,000 insurance policy pay out rests on the investigation. The party had been organised by business partner Finty Lee-Jones and was attended, among others, by Ophelia's stepson, her best friend society photographer Vanessa-Rose, and suspected lover Antonio Da Costa. Ophelia had been spending the company's money, leading to a heated row with her husband the night of her death. Frank and Luella discover Ophelia's morbid fear of water and a previous drowning of a 14-year-old girl 25 years earlier is linked by an identical tattoo on Ophelia and the young girl's back.

Frank and Luella are employed by American private investigator Joe Venice who has been arrested for murder by Sergeant Keeler. He offers them $15,000 to prove his innocence and find an old American car, worth $150,000, for a collector in Hollywood. Frank crosses paths with criminals and boy racers from his past life in the police and discovers the car had been used in a Post Office robbery in 2003. A tattooist injured by the car at the time and a petty criminal watching her lead Frank and Luella to the murderer and the solution of the robbery.

Frank and Luella are employed by Val Twigg to investigate the business model of a rival slimming company, Fatbusters, who has stolen her clients. Luella goes undercover as a client to discover the method used to induce clients to lose weight. The head of Fatbusters is the charismatic Kit Willow who used to work with Twigg and has a new business partner in Diana Winter. One of his clients is "Slim" Jim Sandford who until recently had lost a lot of weight. Another client is Luella's sister Lia and her fractious behaviour is never far away as they are clearing their mother's house approaching the anniversary of her loss at sea. The cleaner at the club also displays irrational behaviour and Frank suspects drugs. When Willow is murdered in a frenzied attack, Detective Sergeant Keeler arrests Twigg as the last person to see him alive.

Frank and Luella are employed by eccentric SciFi author Greg Alban to find the last chapter of his final book stolen in an apparent burglary. Brought to his home by Alban's security guard, their phones are confiscated and they become virtual prisoners. Frank quickly concludes the robbery was an inside job and the 12 stolen pages are in the house with suspects including book editor, accountant, housekeeper, and security guard. Sebastian, unable to contact Frank and Luella, is concerned for their safety and, being rebuffed by Sergeant Keeler, seeks help from Constable Viola Deacon. Sebastian and Viola find the house where Frank and Luella are, just as the housekeeper finds Alban dead with a sword through his body and the missing last chapter. The security guard is missing and Keeler arrests the housekeeper. Luella, reading the last chapter, realises the book characters are based on Alban's staff and a possible motive for murder.

Frank and Luella are employed by Pollie Grisham to find who murdered her boyfriend, actor Dalton Morley, by poisoning at Edie Brosnan's home. They both worked for As You Like It, actors who offer Shakespeare for hire for any occasion. Pollie was the PA to Ava Duffy who was selling the company. Sebastian goes undercover and discovers fellow actor Bernard Wiseau was jealous of Morley. Frank and Luella discover Morley had been given money by Brosnan whose previous husbands died in strange circumstances. Also, Morley had been having an affair with Ava Duffy (unbeknownst to Pollie) and stealing money from the company. Keeler arrests Wiseau as Frank and Luella investigate the tangled web.

Frank and Luella are employed by lottery winner Leroy King, who is convinced his son Arty, who died 5 years earlier in a trainspotting accident, is haunting him. His fiancée Katherine Courazon, a model who met Leroy when she handed him the £36m lottery cheque 5 years earlier, is convinced it was a prankster. Leroy and his son were part of a trainspotting group with Owen Faulconbridge and his son Eddie who met at Arden station. The two families had fallen out over a pact to share the lottery win. Sebastian goes undercover as a trainspotter while Frank and Luella stake out King's house and nearly catch an intruder. When Courazon falls from the footbridge and is nearly killed, attention turns to guilt-ridden Eddie but in the background is the young platform assistant who had a heart transplant 5 years earlier.

Frank receives by smart phone £5,000 anonymously to solve a crime yet to be committed on a walk along Shakespeare's Way organised by Swift Feet Walks. On the tour with Frank are Ben Yang and his wife Chen, a neuro-surgeon; Summer Styles, a prison physiotherapist; and Beverley Sinclair, who was an old friend of organiser Julian Hope. During the first night, Ben Yang is murdered and Sergeant Keeler arrests Frank on the evidence he has. Luella and Sebastian search for a link and learn all the tour party had won the trip as a prize, including Frank who hadn't opened his emails. They then discover Michael Reynolds, a thief who was married to Sinclair and business partner with Hope, who had fallen from a roof escaping from Frank, leaving him paralysed. Released from prison early on compassionate grounds he died within days from complications with his injuries.

Frank and Luella are employed by Arden town councillor, Elaine Davis, to investigate sabotage and threats to humiliate her and her project to replace Christmas with an inclusive Wintermas festival. A misunderstanding between Frank and Luella that one of them is leaving leads to Sebastien being given his first case. Sebastien's case involves graffiti at the house of widower Rob Davenport who is overprotective of his daughter, Olivia, since his wife died. Olivia resents the smothering attention. While Frank and Luella interview suspects, Sebastien realises the two cases are linked but too late to prevent himself and Rob Davenport being held captive in a house unable to get out.