Ben Miller, Sara Martins, Danny John-Jules, Gary Carr and Don Warrington first appeared as Richard Poole, Camille Bordey, Dwayne Myers, Fidel Best and Selwyn PattersonCharlie Hulme (Hugo Speer), a British detective inspector, is found murdered in a locked panic room on the Caribbean island of Saint Marie owned by the Lavenders, Sarah (Coralie Audret) and James (Rupert Graves).
Commissioner Selwyn Patterson demands that a UK officer investigate Charlie's death, so deadpan DI Richard Poole unwillingly flies out to Saint Marie to solve the mystery.
Richard teams up with new sergeant Camille to work out who would want the bride dead; he learns that no one had entered or left the fifth floor of the hotel room during the celebrations, which leads him to believe one of the party guests must be the killer.
However, none seem to have concrete reasons to kill and all have alibis apart from the newlywed husband, after the maid is found strangled, Richard wonders if her cleaning in progress sign caused it all.
When Janice recalls seeing one of the villa's owners leaving the crime scene, Richard begins to question whether June's murder is linked to a historical case back in the UK.
Final regular appearance of DI Richard Poole (Ben Miller) Emma Redding is found dead in her own room at a local retirement home; her death thought to have been suicide.
Humphrey decides he is happier living in Saint Marie, and once successfully solving Emma's death, confides in Fidel about his growing feelings for Camille.
The show introduces Joséphine Jobert and Tobi Bakare as Florence Cassell and JP Hooper and the last appearance of Sara Martins as Camille BordeyA séance is held during the island's Fete Mouri festival, in an attempt to contact a murdered servant from 1850.
The participants are convinced that the ghost of the servant has come back to kill, but Humphrey is not, and begins to seek an alternative explanation for the owner's death.
As Humphrey continues to search for the evidence to pinpoint the killer, he comes across a click beetle which is not native to the island, helping him solve the case.
All the suspects alibi each other, while Lucy also tells Humphrey that she witnessed Tom make a secret phone call and place cash into a moneybag, which has now gone missing.
Local DJ Dezzie Dixon (Terence Maynard) is murdered in a locked room during a live broadcast of his weekly radio programme.
Fellow DJ Bunny Hicks (Errol Trotman-Harewood), who has long waited to step into Dezzie's shoes, soon becomes prime suspect when his alibi fails to stand up to scrutiny.
But as the baffling case tests the team's puzzle-solving skills to the limit, Jack finds himself the subject of an internal affairs investigation, led by DS Madeleine Dumas (Aude Legastelois).
While investigating the case of a man found dead in a boat, Jack has to consider whether to accept Anna's offer to join her on her trip or remain on Saint Marie.
DS Cassell returns to the island to take up the vacant detective sergeant's position offered by Commissioner Patterson who does not mention Parker's idiosyncrasies for fear she would not accept.
The initials "A.S", found wiped in blood on a piano stool, are an important clue and lead to Aidan Shawcross, who supposedly died in a road accident two decades earlier and who had a one night stand with Grace; yet his fingerprints are on the gun that killed Pasha.
Things take a turn for the worse for Catherine in hospital which Camille finds difficult to handle, and she hallucinates DI Richard Poole who was murdered on the island.
Guest appearance of DS Camille Bordey (Sara Martins) Skip Marsden is found with his dinghy on a beach with a harpoon in his chest 11 miles from where his boat was moored at sea by a buoy with four well-to-do drunken stag party members, one a spoiled young viscount soon to be married, on board.
Emmet Peterson staggers into the police station wearing a bloodstained shirt, carrying a pistol and believing that he has shot dead his best friend, businesswoman, Gardenia Dujon.
Things get stranger when a London cab driver, Colin Babcock, receives a Christmas card from Saint Marie claiming Carlton was murdered.
Neville undergoes a crisis of confidence, built upon his previous failure to recognise Sophie's duplicity, and tells the commissioner he intends to leave.
Neville visits Sophie in prison, where he asks if any of their relationship had been "real"; she says she never had romantic feelings for him but had come to like the character she pretended to be when she was with him, so in that sense he'd made her happy.
A celebration of fifty years police service takes an unexpected turn for Commissioner Patterson when he is shot at the local Yacht Club.
After the team arrest Cora's killers and Holly finds her biological mother, Lexi (Ronni Ancona), Commissioner Patterson gets an unexpected phone call from Florence Cassell, who has been living on the neighbouring island of Saint Auguste under a witness protection scheme.
DI Parker chooses to come back for one final case to solve while he comes to realization that Florence may be his true love and must get to the yacht she is scheduled to board before it's too late.
Irate holidaying detective inspector Mervin Wilson is on an early plane home, when his superior calls instructing him to solve the case.
First appearance of DI Mervin Wilson (Don Gilet) Dwayne's replacement police officer and JP's prodigy, Benjamin Brice, is found dead on his first day of work in an assumed biking accident.
Mervin happens to pass the crime scene whilst heading to the airport, and becomes intrigued by the case, especially when clues begin to point to murder.
His first official case is the murder of a finalist on an English adventure game show, who is stabbed mid-zipwire whilst crossing the finishing line.