Someone, a woman or somebody pretending to be a woman, is writing to convicted rapists in prison, befriending them and then brutally killing them when they are released. DI Tom Thorne must discover the link between these killings and a murder/suicide that took place twenty-five years before; a tragedy to which the only witnesses were two small children, now adults and nowhere to be found. How can you escape a past that will do a lot more than just catch up with you?

When he was 12 years old, Adam Ryan went playing in the woods one day with his two best friends. He never saw them again. Their bodies were never found, and Adam himself was discovered with his back pressed against an oak tree and his shoes filled with blood. He had no memory of what had happened. Twenty years on, Rob Ryan - the child who came back - is a detective in the Dublin police force. He's changed his name. No one knows about his past.

In a vicious, calculated murder, a victim is selected at Euston Station, followed home, and strangled in front of her child. When a second body is discovered, killed in the same way at King's Cross station, DI Tom Thorne comes to a horrifying conclusion: this is not one killer, but two.

It was a vicious, calculated murder. The killer selected his victim at Euston station, followed her home on the tube, strangled her to death in front of her child. At the same time, killed in the same way, a second body is discovered at the back of King's Cross station. And this grisly event eerily echoes the murder of two other women, stabbed to death months before on the same day. It is DI Tom Thorne who sees the link and comes to the horrifying conclusion. This is not a serial killer the police are up against. This is two of them - and two killers are way more deadly than one.... 

It's 1996. Detective Sergeant Tom Thorne is a haunted man. Haunted by the moment he ignored his instinct about a suspect, by the horrific crime that followed and by the memories that come day and night, in sunshine and shadow. So when seven-year-old Kieron Coyne goes missing while playing in the woods with his best friend, Thorne vows he will not make the same mistake again. Cannot. The solitary witness. The strange neighbour. The friendly teacher. All are in Thorne's sights. This case will be the making of him...or the breaking.