Detective Inspector Costello has resigned. No notice, no good-byes. Convinced that George Haggerty murdered his wife and son despite his cast-iron alibi, Costello has gone solo, determined to expose a ruthless killer without being hampered by police protocol. But is she right about Haggerty's guilt? And where has she disappeared to? DCI Colin Anderson has no time to ponder the loss of his partner of 20 years. With a badly beaten body found on a remote mountain pass, a woman with a serious head wound who won't communicate in any way and a substantial pool of blood discovered at the edge of Loch Lomond, Police Scotland have their hands full.

A missing private investigator is found locked in a car hidden deep in the woods. Worse still - both for his family and the police - the body was in an area that had already been searched 10 years ago. Detective Inspector Siobhan Clarke is part of a new inquiry, combing through the mistakes of the original case. There were always suspicions over how the investigation was handled, and now - after a decade without answers - it's time for the truth.

Glasgow's citizens are in a celebratory mood for the annual West End Festival parade. But beneath the jovial surface lurks something darker. A confused young woman is found wandering among the stilt walkers and jostling crowds, claiming to have been abducted by aliens. Before DCI Anderson and DI Costello can investigate further, a body is discovered, and it becomes horrifyingly clear that a depraved killer has taken advantage of the busiest day of the year to carry out a gruesomely macabre plan.

In August 1992 a young mother and her two small sons were brutally murdered in the woods behind their home. Her neighbour, Andrew Gyle, was convicted of the crime and sentenced to life imprisonment. Now, 23 years later, a macabre discovery throws new light on the case. Could there have been a shocking miscarriage of justice?

Drawn in by the reputation of the islands, a new English family move to the area, eager to give their autistic son a better life. But when a young nanny’s body is found hanging in the barn of their home, rumours of her affair with the husband begin to spread like wildfire. With suspicion raining down on the family, DI Jimmy Perez is called in to investigate, knowing that it will mean the return to the islands of his on-off lover and boss Willow Reeves, who will run the case.