When the team are called to a flat, they discover three children all dead with a fourth named Callum fighting for his life, DI Ross then discovers the dead body of the children's father Pete in the bathroom, he therefore becomes the prime suspect but then when forensic tests reveal that Pete died before his own children. The real culprit is still at large and shocks all of the team.

After the badly beaten body of a man is found dumped on a motorway underpass, his murder is linked to a Fight Club style bare-knuckle boxing venue. Both professional and personal lives collide at Maryhill CID, with one of the detectives having to come face to face with their own demons.

When a busker is fatally stabbed in Glasgow city centre, the newly promoted DI Jackie Reid heads up the investigation. Mita Rahim joins the Maryhill CID team properly while DI Ross suffers a personal heartache.