Detective Grace Macallan is at crisis point. She's unsure of her future, of whether she has the strength to continue with her role in serious crime. Events are threatening to run out of control, and this new investigation will test her to the limit.

An undercover officer is missing and a woman is washed up, traumatised and barely alive, on the shores of Berwickshire. She has witnessed horror on the dark waters of the North Sea, and her subsequent ordeal to survive turns her life into a nightmare.

As she untangles the woman's story of trafficking and abuse, Grace is drawn into the world of organised crime in Newcastle, Glasgow and Edinburgh. At their head is Handyside, a brutal gangland boss who's fought hard and dirty to control his territory. But there's a traitor in his midst, and soon the most cold-blooded criminals in the North East of England and Central Scotland turn on one another in a desperate race to destroy the evidence that will lead Grace to them.

Grace must pit her wits against Handyside, knowing he'll stop at nothing to protect his criminal empire. She knows, too, that one wrong move could end in tragedy.