Plot
Twenty-two years prior to the novel's events, twelve-year-old Adam and his two best friends failed to come home after playing in the familiar woods bordering their Irish housing estate. The Gardaí find Adam shivering, clawing the bark of a nearby tree, with blood in his shoes and slash marks on his back. His friends are never found. He is unable to say what happened to them. Now using his middle name, Rob, he is a detective with the Murder Squad. His amnesia holds to the present day.
The plot of the novel circles around the murder of a twelve-year-old girl, Katy Devlin, whose case Rob and his partner Cassie Maddox are assigned to investigate. The body is found in the same woods where Rob's friends disappeared, at an archaeological dig site, and the coincidence is enough to make Rob nervous, though he insists to his partner that he is fine.
Cassie and Rob have been partners for a few years and get along famously, teasing one another and completing one another's thoughts. Cassie is one of the few people who knows the truth about Rob's past. There are many rumours that they are romantically involved, though both of them scoff at the idea, despite the fact that they live almost like a married couple, spending a lot of time at Cassie's cooking dinner for one another, drinking wine, and having Rob crash on Cassie's couch across the room.
Katy's murder takes the pair along many lines of investigation. Her death might be related to her father's protests against the new motorway meant to go straight through the dig site, or one of the students on the dig might have attacked her. She might have been abused by her father or someone else (her mother, twin sister, or older sister) in the family. She might have been previously poisoned over time. Or it might be related to the disappearance of Rob's friends, as a hair clip that one of his friends was wearing that day appeared near the crime scene.
These possibilities are investigated, but the detectives come up frustratingly empty-handed at every turn. The case messes with Rob's psyche as he tries to remember details about the two previous disappearances in case it would help. He tries spending the night in the woods, but freaks out and calls Cassie to pick him up. He's afraid to sleep again, thinking that he'll just have nightmares, and asks Cassie if he can sleep in her bed. They lie awake for a while. until Rob kisses Cassie, and she reciprocates.
Rob feels immensely awkward after and can't go back to their normal jokey-insult ways, but he also feels that he can't start a relationship with her. Their partnership deteriorates just as they start to uncover new leads in the case, and they are unable to discuss the case and get along the way they used to.
Rob goes back to the dig site alone, where all the students are frantically digging before the site is shut down for the construction of the motorway. He comes to a realisation and calls in the forensics team again, who discover the location of the murder in a shed to which only three people have the key. After some heavy interrogation, one of the suspects confesses, though his motive is far from clear.
It becomes clearer when the suspect contends that he had been dating Katy's older sister, Rosalind. When questioned by Cassie, Rosalind denies it and any involvement in Katy's death, but she also makes a comment that Cassie is obviously sleeping with Rob. Cassie takes it in stride; but, after the interrogation, she has an idea of how to get a confession out of Rosalind: Go to her and admit sleeping with Rob and promise to keep her updated on the case if she promises not to tell.
Rosalind's psychopathic tendencies get the better of her; and, once she knows that she has Cassie in her debt, she brags about the whole thing and how she got the murderer to come up with the idea by telling him that all three girls were being sexually abused by their father, but that Katy liked it and was therefore their father's favourite. Rosalind also told him that Katy told their father lies to make him beat them and would watch and laugh and that, if Katy were gone, then they would be happy. She also admitted to Cassie that Katy was strong-willed and wouldn't always do as Rosalind told her, so she had poisoned her to make her sick. After this confession, recorded on a wire, Cassie arrests her and takes her in; but, because Rosalind was a few months from turning 18 (though she had told Rob previously that she was already 18), the confession is invalid. She is released with a smug smile.
The Murder Squad Superintendent has learned that Rob is actually Adam Ryan and transfers him to menial desk work in the General Unit. He never returns to the Murder Squad. Cassie starts dating another member of the squad and eventually becomes engaged. Rob is heartbroken and calls her, but it's too late. He goes to the dig site to see the motorway construction has begun and thinks that he'll never regain his lost memories of that night.
