[Belladonna (Atropine), in The Labours of Hercules].

The Labours of Hercules, written by Agatha Christie, contains twelve short stories, with 'atropine' playing a crucial role in the seventh story, The Cretan Bull (1939). Atropine easily crosses the blood-brain barrier (BBB), leading to central nervous system (CNS) side effects such as delirium, hallucinations, disorientation, memory problems, coma or stupor, and convulsive seizures when overdosed. In this episode, a concentrated form of atropine obtained from prescribed eye drops was misused to induce a hereditary incurable neurodegenerative disorder, similar to Huntington's Chorea, in the client's fiancée. However, Mr. Poirot discerned this by careful examination of his symptoms and resolved the case.