A two-part adaptation of the Iain Banks novel of the same name, "Stonemouth" is a rite of passage tale set in the fictional Aberdeenshire village of Stonemouth which follows Stewart Gilmour (Christian Cooke), who returns to the village for his best friend's funeral. Run out of town a year earlier by his girlfriend's family, Stewart is forced to face up to his own past whilst uncovering the sinister truth behind his friends apparent suicide.

Stewart's abductors release him from the bridge but warn him to leave Stonemouth. Later, preparing for Callum's funeral, he learns that his father has indulged in lucrative smuggling and at the funeral itself he again quizzes Grier and finds that she told Don about her affair with Callum. Having seen CCTV footage of Callum on the bridge shortly before his death he convinces Ellie that her brother was murdered and they learn that there is a wide-spread smuggling operation in the town, led by Mike in which Callum was also involved. Together they infiltrate Mike's ...