Following the murder of coastal town businesswoman and am-dram theatre director Menna Hughes, Janie is eager to solve the case and land the DI promotion she desperately wants. She enlists John's help, but bristling at Janie's insinuation that he might have ‘lost' his acting chops, John takes matters into his own hands and joins the cast of the theatre group's next play. What starts out as a murder investigation soon becomes a cathartic journey for John, who is unexpectedly reminded of why he fell in love with acting in the first place. As for Janie, witnessing a downtrodden suspect finally stand up for themselves inspires her to confront her own demons from the past.

Janie has been avoiding John ever since Clarke learned the truth about their partnership and put her promotion on ice. But an unexpected gesture from Clarke's boss sees John's role as a consultant with Mid Wales police made official. This forces John and Janie to find a new normal and rekindle their connection. They're tasked with solving the murder of Janie's mechanic, Dean Ward, which took place during a school reunion party at Janie's old school. As John and Janie dig deeper into Dean's death, links emerge to DC Chaudhry's recently unearthed cold case, a body uncovered in a drain. This forces Janie to revisit the events that led to her teenage best friend Sian's suicide fifteen years ago. John's instincts about the case puts him and Janie at odds, eventually forcing them to acknowledge the importance of their friendship. But as the series comes to an end, John upends their reconciliation with unexpected news…