Mary Chilcott

In the short story The House of Lurking Death, Mary Chilcott went to school with Lois Hargreaves. She lives with Lois at Thurnly Grange. She survived the mass poisoning episode at the Grange because she hates fig paste. Tommy and Tuppence consider her a plausible suspect in engineering the killings because she does not appear as upset about the event as she ought to be. Then again, if she had done the poisoning she would feign innocence by making a point of being upset. Suspicion is further heightened by the fact that Miss Logan had loaned Mary an old book on drugs and herbs Materia Medica. Miss Logan said she had a private kitchen where she brews liqueurs and preserves in the old fashioned way. Mary had been interested in herbs and had conducted some experiments in Miss Logan's kitchen.

Mary is described as "tall, with a tanned face, and steady blue eyes." Tommy observed that she is "extremely capable and businesslike--perhap a shade too much so--but very reliable."

Portrayals
In LWT's 1983 TV adaptation of The House of Lurking Death, Mary Chilcott is portrayed by Louisa Rix. The portrayal is faithful to the original but here she has a larger role. She is pursuing a relationship with Dennis Radcliffe and in so doing is also undermining her friend Lois who is also in love with him. In one scene, Mary asks Radcliffe when he intends to tell Lois about them. This, and the fact that she remains calm about the deaths in the house make her even more of a suspect. In one scene, Tommy actually accuses her. In this adaptation, it is also Mary who comes into the room and witnesses the confession during the climactic scene when Tommy and Tuppence unmask the killer. In the original, it was Dr Burton who came in.