Flavia de Luce didn't intend to investigate another murder--but, then again, Rupert Porson didn't intend to die. When Porson's van breaks down in Bishop's Lacey, he becomes the victim of an electrocution too perfectly planned to be an accident. And it's possible that his killer may lure in Flavia way over her eleven-year-old head, to a startling discovery about the chemical composition of vengeance.