Dr Tony Hill finds his work with the police compromised when a student from his university is abducted. But that's not his only worry - Carol stops trusting him when he allows one of his own pupils to help with the investigation. Dr Tony Hill finally persuades the police to reopen the case of Maggie Thomas, his long-standing child killer patient, in order to try and recover the bodies for the victims' families. Carol is less than impressed to discover that Tony has enlisted the help of one of his students, the bright and extremely attractive Laura Webster. But Laura's abilities at criminal psychology become challenged when her best friend Hattie is abducted. Tony finds that the price for bending the rules with Laura to help her understand crime on the Maggie Thomas case gives her too much access to the work to find her friend. Loyalties fray as Tony finds himself in the middle of the unpredictable triangle of himself, Carol and Laura - and in so doing leaves Maggie alone and vulnerable, haunted by the ghosts of the children she murdered. Meanwhile Hattie's abductor has struck again, and while police attention focuses on that, Maggie decides that she's had enough of not being taken seriously and Carol finds herself with another victim on her hands.
When the bodies of recent murder victims are dug up with ancient remains in the grounds of a ruined Abbey, Tony and Carol uncover more local legend than fact. But will that lead them to the killer? When bodies are discovered at Norton Hotel during the digging of new foundations, Carol is sent in to oversee whether they were in any way suspicious, or a legacy of the hotel's previous incarnation as part of the local Abbey. But the discovery of the bodies coincides with the hotel being burned to the ground, and Carol realises that she's got a very current case on her hands. She calls Tony in when it becomes apparent that someone is killing people in a way that Norton hasn't seen since it burned witches back in the middle ages. Needless to say, Brandon isn't too chuffed to have nothing to brief the press with apart from Tony's theory that the same killer could somehow be reaching a long arm over five centuries of murder. Tony and Carol are forced to challenge all that they thought they knew, as it is a case rich in the inexplicable. This killer forces them to test not only their science and experience, but also their very beliefs.
Tony and Carol trace two murders to one suspect but then find that he is in prison. Carol is upset by Tony's wedding plans. An arrest goes awry. Tony asks Carol to perjure herself.
Bradfield is in panic as someone preys on its most vulnerable - its hospital patients. Carol must juggle how to warn the public and how to keep a predatory MI5 official at bay. The only way out is to solve the case fast - but there is very little to go on, even for Dr Tony Hill. Carol's investigation into a domestic murder takes a darker twist when the victim, who had been recovering well in hospital, is murdered. As a precaution she orders post mortems of other patients who had died in that hospital of "natural causes", and finds out that she has a lot more murder on her hands than she'd bargained for. Tony suggests the killer may believe he is healing victims in some way, killing for religious belief - but the thought of a compulsory euthanasia killer brings little comfort to the investigative team, or the victims' families. Tony and Carol begin to unearth the undercurrents and tensions that lie within the hospital structure, but that only yields more suspects, rather than narrowing the search. MI5 get involved when Islamic terror becomes one of the lines of inquiry. Carol has another layer of command that has to be constantly satisfied, and when Brandon falls ill, Carol loses her only political protection. Tony and Carol must follow their instincts, but with Merrick and Kevin competing for Carol's old job of DI, they've got no one but themselves to turn to for help.