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.

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.