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.

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.

Hogmanay. New Year's Eve. A dead teenager, another missing. One hell of a case. Meet DS Vicky Dodds. Settling down for a nice Hogmanay with her daughter and her best friend, a phone call pulls DS Vicky Dodds into work and to a deadly new case. A teenage girl, her body cooling in a cold, dark supermarket car park. Found next to her friend’s car, but the driver’s missing too — has the killer taken her? Or is she the killer?

A woman is found in a local cemetery, crushed to death under a gravestone. A production company is there, filming the remake of a classic sci-fi TV show on the grounds, making the investigation more difficult for DCI Harry McNeil. It's his first day in charge of the cold case unit in Edinburgh. After spending four years in Professional Standards, he has little choice but to take the promotion.

A mutilated body is found dumped at Cowane's Hospital in the heart of historic Stirling. For DCI Malcolm Ford it's like nothing he's ever seen before, the savagery of the crime making him want to catch the murderer before he strikes again. For reporter Donna Blake it's a shot at the big time, a chance to get her career back on track and prove all the doubters wrong. But for close protection specialist Connor Fraser it's merely a grisly distraction from the day job.