Nikki Alexander finds herself working on a case from her past. Four years previously, she had been instrumental in getting 17 year-old Anna Holland acquitted of a murder charge. She had been accused of egging on her boyfriend in the murder of a young mother they chose randomly. Now, while under police protection, her body has been found in a burnt car. The autopsy reveals that she had been stabbed but had died from carbon monoxide poisoning and so was burnt alive. Nikki also receives a surprise visit from her estranged father who wants her to perform a second autopsy on a friend who recently died.

Nikki Alexander begins to have serious doubts about her conclusions four years previously when her testimony helped acquit 17-year-old Anna Holland of murder. Anna's mother had withheld information from the police and as Nikki reconstructs the scene of the crime, she realizes that the blood spatter evidence no longer holds up. The police focus on the dead woman's husband but the pathologists find that a series of unsolved murders may have a bearing on the case. Nikki is also annoyed with her father, who has conned Harry Cunningham into completing a second autopsy on his late wife.

The body of young Colin Connor is found in an attic at a former hospital now marked for residential development. He had been stealing metal but was locked in the attic by his accomplice who then fled. The culprit seems to be Derren Blackburn whose father lies for him when D.I. Cherry visits with Jack. At the same time, Leo is asked by distraught father Tom Hancock to conduct a post mortem on his son Peter, who, Tom is convinced, died because of electrical towers outside his window. Leo is surprised to find that Peter and Colin had an identical kind of kidney dysfunction. James Embleton, a government minister who begins dating Nikki, is in charge of the hospital conversion, and is visited by the sinister David Loader, who warns him of Leo's investigation into Colin's death. Leo and Jack look for proof of toxicity at a farm near the hospital, but are evicted by the army. Leo contacts George Ryder, who owned the farm, and they agree to meet at the hospital as George has an important revelation, but tragedy intervenes.

After Darren is killed trying to escape, his father tells Leo of the boy's recent personality change, and examination of his body shows he had Fanconi's Syndrome like Colin and Peter. Nikki tells James that Leo suspects a conspiracy, especially after George's daughter has spoken of the haste with which the family was moved from the farm and the poor compensation they received. James now comes to see that his father, Sir William, and his henchman Loader - who Jack proves killed George Ryder - are involved in a cover up. After being falsely discredited and suspended from work, Leo joins Tom to investigate the woods near the farm and hospital and discover what the cover up had been trying to hide. As Nikki asks James how much he knew, Tom sets out for revenge.