When babysitter, Jessica Lake, is discovered dead, it immediately throws up a number of questions for Lewis and Hathaway. Was the killing opportunistic or calculated? Was Jess actually the intended victim, since Nick and Honey Addams were supposedly due to return that evening, plus their regular babysitter cancelled at the last minute? And finally, why was she tied-up post mortem?
As our cops delve deeper they find themselves in the world of suburban swinging - with the Addams' alibi being Nick's smarmy nouveau-riche boss Tom Garland and his wife, Davina. They also find a photo of Jess with her elbows and wrists elaborately bound behind her, which leads them to fetish photographer, Marion Hammond.
Meanwhile, Jess's boyfriend, Gideon Massey, informs them that Jess had been squatting in an abandoned children's home, Boxgrove, where she grew up in care. Lewis and Hathaway visit the eerily empty building, and find Jess's housemates Kyle and Silas, whom they inform of the murder. Silas takes it particularly hard.
Following up Gideon's alibi for the night of the murder, Lewis encounters Dr. Robert Massey, an Ethologist at the university's primate lab, where he studies communication between monkeys. Meanwhile, Hathaway visits the Ashmolean to interview Gideon's mother, Constanza, who is busy preparing for Marion's new exhibition - featuring pictures of Jess - and has little interest in Jessica's death. Silas, on the other hand, has become fixated on the murder, and, inspired by his favourite comic book hero, he endeavours to track down the killer himself.
Unfortunately, the morning after he sets off on his quest, he too is found dead - tied to a tree, shot through with spikes, in the pose of St Sebastian. It is another Marion Hammond homage. And his body is found just yards from her flat.
After Silas's death, the investigation steps up a gear. Hathaway discovers that years ago, Constanza Massey used to work at Boxgrove. It was her fortnightly "escape" from the son with whom she was never able to bond. She reveals to Hathaway that she hated Jess because she was a constant reminder of those days; and her failure as a mother. Also, on further questioning of the Garlands, Lewis discovers that Nick Addams' alibi isn't quite so watertight as he had them believe, but is he capable of murder?
When Hathaway unearths a vital clue it's up to him and Lewis to catch the murderer before any more harm is done.