Tony suspects a serial killer is luring dejected children to their deaths when the bodies of three young boys are found in different places in Bradfield. Each of the victims had suffered maltreatment. As it becomes more obvious that these victims are being placed at very specific sites, Tony comes to realize that the killer is trying to tell police something about their past. When a child is found in a deserted warehouse, dead through an overdose of sedatives, nobody knows whether it's suicide or murder. Carol calls Tony in to advise, then a mugging leaves her in hospital. Her new boss Eden puts Kevin in charge of the case. As two more missing children are found dead in different locations, it becomes apparent that these victims are being placed at very specific sites. Tony realises that the killer is trying to tell police something about their past. Tony's deduction that the killer is luring unhappy children into trust focuses suspicion on local minister Michael, whom Tony suspects of abusing a young acolyte, Julie. But even when Michael is arrested the murders continue, and Tony begins to suspect that these are crimes of love and loyalty - a killer who believes they are righting wrongs and continuing work begun in the past. Now, with Michael's Christian website at the centre of the investigation, Tony must pose as a young victim to save the latest abducted boy. Carol must trust Tony, the killer must believe Tony, and Tony must trust Julie as he enlists her help to ensnare a murderer who believes they are alleviating suffering even as they kill.

When a series of vicious murders sends the town reeling, Tony becomes consumed with the notion that they are the work of killer William 'Mack the Knife' MacAdam. Newly-released back into society after being educated during his long sentence, MacAdam is now enrolled as a Ph.D. student in Tony's university class and seems overly keen to take his place as media pundit on serial killer cases. Tony's torment is worsened when he clashes with Carol over her desire to have a baby before it is too late. But could fertility be the key to solving the crimes?

The brutal murder of a woman, beaten to death with a steam iron, brings Tony back from a publicity tour for his latest book to join in on Carol's investigation. More bizarre but completely different deaths follow, and Tony is bewildered, unable to create a profile for a seemingly schizophrenic killer. As he is stalked by a Canadian woman he met on the book tour, Tony realises they must focus on the relationships at work behind the crimes. Tony is not behaving well during a publicity tour for his latest book and Carol is causing ructions during a case review in York with her unsympathetic new boss Eden, when a bizarre murder intervenes to bring them home. Further deaths follow but the MOs are all so strange and so significantly varied that profiling suggests each one must be committed by a completely different person. And to make things more complicated the killer appears to be schizophrenic - both violent and childlike at the same time. Tony is baffled. Eden is piling on the pressure. And there's pressure of another sort when Tony attracts the unwanted attentions of Patricia, a Canadian woman he met during his book tour. Caught in a triangle between a potentially violent suitor and unwitting obstacle Carol, Tony discovers that the killings also reflect a triangle forged in repression and juvenile abuse. Tony and Carol must separate the method from the madness to understand the relationships at work behind the crimes. And Tony is forced to question just how equal his relationship with Carol really is. With Eden threatening action that Tony knows will lead to carnage, can he and Carol act in time to stop the killer from turning on his most longstanding victim, the person he ought to love?

Tony faces his own mortality when he is diagnosed with a brain tumour after being hit on the head by a criminal. While assisting Carol on an investigation into an anonymous sniper who is picking off victims in the city street, his behaviour becomes more erratic and his wild theories make Carol wonder if his health is making him unreliable. In a city gripped by fear, can random forces and chance save Tony - and help them catch this unpredictable killer? Hit on the head by a would-be murderer caught by his clever psychological outmanoeuvring, Tony wakes up in casualty to discover he's got a brain tumour. His behaviour doesn't initially strike Carol as particularly odd - he's always been eccentric - but the doctors say it's down to chance whether his bizarre symptoms signify something fatal. While Tony faces his own mortality, an anonymous sniper picks off victims in the city streets. Despite every investigative effort the sniper eludes capture and the deaths seem meaningless and motiveless. The invisible killer seems to be taunting the police. Carol wants Tony's input but his theories about quantum physics and chaos seem wild enough to suggest he's becoming unreliable. As the deaths continue, Tony's behaviour becomes more erratic, the city is gripped by fear, and Carol faces an angry press. Trying to understand this killer forces Tony and Carol to question everything they've learned, until Tony accepts that his own fate is governed by random forces and realises that the killer's actions are dictated in the same way. Only by giving in to the laws of probability can he and Carol hope to catch the killer. And only by putting his own life on the line and trusting his psychological intuition can Tony gamble on survival.