Mrs Pengelley

In the short story The Cornish Mystery, Mrs Pengelley was the wife of Edward Pengelley, a dentist in the Cornish town of Porgarwith. She approached Poirot for help because she thought her husband might be trying to poison her. She was sick almost after every meal but this did not happen whenever her husband was away at the weekends. There was also a tin of weed killer which her husband had bought. The gardener said it was never used yet it was half empty. Mrs Pengelley thought her husband's motive was a "yellow-haired hussy", the dental assistant, Miss Marks, whom Edward employed in his clinic.

Poirot found Mrs Pengelley credible. She did not strike him as a hysterical type. He agreed to take up her case and travelled to Polgarwith with Hastings. However, he arrived too late, as Mrs Pengelley died just half an hour before they reached her house.

Portrayals
Mrs Pengelley was played by Amanda Walker in the film adaptation of the story in episode 4 of Series 2 of ITV's Agatha Christie's Poirot drama series. In the original story, Mrs Pengelley had no money of her own. In the adaptation, her will left most of her wealth, amounting to some twenty thousand pounds in bonds, to her husband. This provided another motive and grounds for suspecting him of the crime.