When a much-loved child disappears with his minder, Lawrence Harpham follows the trail to Battersea. Meanwhile, Violet investigates a thirty-year-old Suffolk poisoning. With suspects thin on the ground, Violet must use every means at her disposal to solve the mystery. Can Lawrence's close encounter with a callous serial killer provide clues to her investigation? And will their increasingly fractured relationship stand in the way of progress? As the two mysteries converge, Lawrence finds himself at the mercy of a predator. Can he survive and will he ever see Violet again?