Strychnine

Strychnine is a highly toxic and colorless alkaloid. It is also odorless. When swallowed or inhaled, it can cause death by asphyxia. It is often used to kill small animals, including mice and birds.

Characters poisoned with strychnine

 * Mr Appleton - The Coming of Mr Quin
 * Miss Amelia Barrowby - How Does Your Garden Grow?
 * Lady Ariadne Grayle - Death on the Nile (short story)
 * Emily Inglethorp - The Mysterious Affair at Styles

Non-canonical characters poisoned with strychnine

 * Èmilie Beauregard (parallel of Emily Inglethorp)