Leo receives devastating news from home - his wife and daughter have been involved in a hit-and-run accident, prompting him to set off for Sheffield immediately. Meanwhile, Nikki is called out to the river when the bodies of two unidentified women are discovered, both shot execution-style.

The team are called to the scene of a drive-by shooting, but the case proves less clear-cut than expected when evidence emerges that someone returned fire. The vehicle used is soon traced to an abandoned industrial unit, where a decomposing corpse is uncovered - and Nikki resolves to find out the true cause of death.

A girl, Lucy Philips, has been kidnapped, but when her father tries to give the money to the kidnappers it is not collected. Later the girl's body is found in a storm drain pipe. It turns out she was killed before the ransom note was even delivered. Harry visits the scene where a young woman, Dawn, has died in three inches of water in a paddling pool, and her expensive necklace has disappeared. The team start to suspect the two women have been killed by the same person. Could there be a serial killer on the loose? Dawn's sister contacts the police. The expensive necklace has been found in her daughter's toy box. Harry realises that there has been no murder, the death was just a tragic accident. Meanwhile Nikki is determined to track down the murderer of Lucy Philips, even if she has to come face to face with the murderer himself.

The team pursues a serial killer with a grisly desire to look at his victims' faces as they die, and the trail leads into the world of academic philosophy. However, Nikki is distracted from the case by the death of her grandmother, while Harry investigates the demise of a woman who apparently drowned in three inches of water.

Nikki investigates a man's apparent suicide and begins to suspect foul play after two more deaths occur, leading to recently released mental patient David Nicholson being accused of their murder. While the doctor treating Nicholson is adamant that he is no threat to anyone, the pathologists are not convinced - especially when a connection with the original victim emerges.