Abel learns that his girlfriend, Marianne, is leaving him for his best friend Paul, who is the father of her child. Seven or eight years later, Paul dies and Abel and Marianne resolve to restart their relationship as she and her son Joseph move in. Joseph claims that his father died because Marianne poisoned him. Abel is also sought after by Ève, Paul's younger sister who has been infatuated with Abel since she was 14 years old. When Ève directly tells Marianne to leave Abel or "it's war", Marianne prompts the confused Abel to sleep with Ève. Now caught in a difficult situation between two women and a young boy with an eerie fixation on murder, will Abel keep his relationship with Marianne intact?
On the review aggregator website Rotten Tomatoes, A Faithful Man holds an approval rating of 81% based on 57 reviews, with an average of 6.7/10. The website's critics consensus reads, "A Faithful Man's lack of tonal commitment may frustrate, but the end results should still prove entertaining for viewers in the mood for a French romantic farce."[12]Metacritic, which uses a weighted average, assigned the film a score of 67 out of 100, based on 15 critics, indicating "generally favorable reviews".[13]