Across the series, key twists define character journeys and narrative continuity:
- Season 1–2: DI Richard Poole establishes his brilliant detective presence while secretly developing feelings for DS Camille Bordey.
- Season 3 Shock Opener: Richard Poole is murdered during a Cambridge alumni reunion by fellow student Sasha Moore (who was actually Helen Reid, an impostor concealing identity theft). DI Humphrey Goodman arrives, solves Poole's murder, and settles on Saint Marie.
- Season 6 Mid-Season Departure: While investigating an interrelated case in London, Humphrey reunites with Martha Lloyd and decides to stay permanently in England. DI Jack Mooney takes over the Saint Marie post.
- Season 8–9 Turning Points: DS Florence Cassell suffers personal tragedy when her fiancé Patrice is murdered, leading to her temporary departure. DI Jack Mooney later leaves after finding peace with his widowerhood. DI Neville Parker arrives in Season 9, initially complaining about every tropical element.
- Season 12 Framing Arc: Neville is framed for murder by Sophie Chambers (Rebecca Wray), a vengeful woman from his past, forcing the Honoré team to race against time to exonerate their own inspector.
- Season 13 Culmination: In the 100th episode, Commissioner Selwyn survives an assassination attempt. In the Season 13 finale, Neville Parker finally embraces love and departs Saint Marie on a passenger ferry alongside Florence Cassell, ushering in DI Mervin Wilson for Season 14.