The police apprehend a gang of opium smugglers on the banks of the Thames, but as he stands at the water's edge, Inspector John Marlott makes a shocking discovery. The body of a dead child is washed up on the shore, but further examination of the corpse reveals a grotesque state of mutilation. Home Secretary Sir Robert Peel orders Marlott to lead the investigation, while details of the investigation must remain confidential.
After his discovery on the banks of the Thames, Inspector Marlott visits the house of artist and printmaker William Blake, who is on his deathbed. Later, Marlott confers with Nightingale, a local policeman who has been keeping watch on The Fortune of War, a public house where body snatchers are known to gather. The pair create a plan to capture a person of interest who may be able to aid them with their investigation.
Marlott takes a terrified Pritty to meet the men who kill for money, and they find themselves in the tunnels under Smithfield market which run from the Fortunes of War pub to St Bart's Hospital. Meanwhile, Flora returns to Marlott's lodgings - however, he plans to use her as bait for the murderous gang, against the wishes of Nightingale.
Boz publishes a newspaper article about the murders and causes a public outcry, while Mary Shelley, the author of Frankenstein, follows her own line of enquiry into the medical practice of Sir William Chester. Elsewhere, Marlott decides to go back to Greenwich where it all began to see whether he is missing something.