The Sicilian Defence (S15E04)

Harriet Farmer awakens from a coma following her near-fatal elopement attempt. Shortly after, a series of murders strikes a local chess club, raising suspicions. Detectives John Barnaby and his team delve into the connection between Harriet's past attack and the recent killings, exploring the strategic parallels to chess moves. As they unravel the mystery, they also seek to uncover the fate of her boyfriend, Finn, who has been missing since the incident.