A turf war between two bakers leads to food poisoning at an amateur dramatic society.

On route to Gemma and Terry's wedding, Gemma diverts them to a mystery at a couples therapy retreat where death threats have been received. The unusual therapy practices put a strain on their relationship as the body count grows.

Terry and Gemma finally arrive at the hotel 48 hours before their wedding to finalise their preparations and relax in the spa. The weekend soon takes a turn when they discover a dead wedding guest.

A twisted serial killer is on the loose and only Terry and Gemma's coach tour knowledge can help the police find the murderer.

With Terry and Gemma's relationship on the rocks, Terry is forced to reconnect with his old friend Willy Watkins, leaving Gemma to investigate crimes solo - until Monica gets in on the act. Their hunt leads them to things in Terry's past.