London, 1851. Restless and bored after a long hot summer, apothecary and poison expert Jem Flockhart decides to redesign her physic garden. But plans are thrown into confusion when a man's skeleton is unearthed from beneath the deadly nightshade, a smaller, child-like skeleton curled at its feet. The body bears evidence of knife wounds to its ribs and arms, and is accompanied by a collection of macabre objects: a brass bowl, a curious coin-like token, a set of tiny ivory sculls.

The police claim the victim is too long-buried for answers to be found, but for Jem, a corpse in her own garden is something that cannot be ignored. The plans to the garden, laid out some forty years earlier, reveal a list of five names.

When Jem and Will start asking questions, the murders begin. Each victim has a past connection with the physic garden; each corpse is found with its jaw broken wide and its mouth stuffed with deadly nightshade. As they move closer to uncovering the truth Jem Flockhart and Will Quartermain encounter a dark world of addiction, madness, power and death that strikes at the very heart of Jem's own history. This time, the poison is personal.