Ailsa Connolly was a brilliant psychologist and a respected criminologist. She was also a serial killer. Six years ago, DCI Sean Bracken caught her just before he was about to become her seventh victim. Every year on the anniversary of her incarceration, she taunts him with a phone call, giving him one message: "When I get out, I'll kill you." Now, Bracken has transferred back to Edinburgh and is thrown into the deep end on his first day back on duty. There's a killer who is emulating Ailsa, threatening to surpass her body count.

Former soldier. Ex-copper. Current man on the edge. Shunned by his old colleagues, and dividing his time between a dead-end job and the bottom of a whisky bottle, former Police Scotland detective superintendent Bob Hoon’s life is a mess. Then an old face from Hoon’s Special Forces days turns up asking for help: His teenage daughter has been missing for months, the police have drawn a blank, and he needs the kind of help that only Hoon can provide. And besides, Hoon owes him one.

Met cop DI Rob Marshall is hot on the trail of the serial killer known as the Chameleon, who has abducted, tortured and killed a series of young women in Northwest London. As they close in, the Chameleon—who switches identity to get close to his victims—shoots Marshall’s partner and escapes.

Five years ago, DCI John Lomond led the search for notorious Glasgow child-killer ‘The Sandman', until personal tragedy forced him off the case. In Lomond's absence, the killer was never found. Now, with nothing but work left in his life, Lomond remains obsessed with the case–despite the nightmares it brings. When a child is abducted in similar Sandman fashion from an affluent Glasgow suburb, Lomond is brought in to find them before it's too late.

Was the biggest case of his career the worst mistake he ever made? Ten years ago, DCI Jack Logan stopped the serial child-killer dubbed "Mister Whisper", earning himself a commendation, a drinking problem, and a broken marriage in the process...When another child disappears a hundred miles north in the Highlands, Jack is sent to lead the investigation and bring the boy home. But as similarities between the two cases grow, could it be that Jack caught the wrong man all those years ago?