When Dr William Macbeth poisoned two of his sons in1927, his wife and sister hid the murders in the intensely private realm of family secrets. Macbeth behaved as if he were immune to consequences and avoided detection and punishment.

Or did he? Secrets can be as corrosive as poison, and as time passed, the story of Macbeth haunted and divided his descendants. His grand-daughter, Gail Bell, spent ten years reading the literature of poisoning in order to understand Macbeth’s life. Herself a chemist, she listened for echoes in the great cases of the nineteenth century, in myths, fiction, and poison lore.

Intricate, elegant, and beautifully realised, The Poison Principle is a book about family secrets and literary poisonings.