Who killed David Cartwright in Death in Paradise? A detective took the blame

David Cartwright, the smugly brilliant criminologist played by Patrick Kennedy in Death in Paradise series 12, was murdered by Sophie Chambers — DI Neville Parker's own girlfriend. And Neville himself was arrested for it.

Cartwright killed Jake Dalton first

Before anyone killed Cartwright, Cartwright killed someone else. Water taxi driver Jake Dalton was stabbed to death in his own home on Saint Marie — and Cartwright did it purely to see if he could get away with it. A former university criminologist who'd been forced out of academia after becoming dangerously obsessed with a serial killer he was studying, Cartwright had retired to the island with a warped new fascination: what it would feel like to murder someone himself.

His method was fiendishly clever:

• The alibi — he arranged a live video Q&A to run at the exact time of the killing.
• The misdirection — he slipped out while his cleaner Rose Dalton thought he was in his study, murdered Jake in Rose's own house, then hosted the Q&A from the crime scene — redecorating the wall behind him to match his study.
• The taunt — he sent Neville a letter in advance, warning him a murder would happen that day. Just for fun.

Why Neville was arrested

Neville (Ralf Little) worked out that Cartwright was the killer. The problem: no hard evidence. Cartwright knew it too, and goaded Neville by sending him a signed copy of his book. Furious and out of options, Neville stormed over to Cartwright's hotel room to confront him.

The next scene showed Commissioner Patterson and the team processing the room as a crime scene. Cartwright was dead on the floor. Neville was the only person seen entering the room. He was arrested and charged with murder.

Who really killed him?

In the following episode, "Sins of the Detective," DI Karen Flitcroft flew in from London to investigate. Commissioner Patterson, convinced of Neville's innocence, ran a parallel inquiry and uncovered the truth.

Sophie Chambers (Chelsea Edge) — the English traveller Neville had been dating since the Christmas special — wasn't who she claimed to be.

Her real name was Rebecca Wanslow. Years earlier, Neville had arrested her sister for murder back in Manchester. The sister subsequently took her own life in prison. Sophie came to Saint Marie under a fake identity, engineered a relationship with Neville, and killed Cartwright specifically to frame him.

Justin West, previously linked to Sophie, was discovered to have broken into Neville's residence as part of the setup. The whole thing — the romance, the friendship, the trust — was a long con.