In the novel The A.B.C. Murders, Mrs Marbury (née Smith) is the landlady of Alexander Bonaparte Cust. She has a daughter named Lily and a brother called Bert.
Portrayals[]
In the film adaptation of The A.B.C. Murders in Series 2 of ITV's Agatha Christie's Poirot, the part of Mrs Marbury is played by Lucinda Curtis. Cust does tell her he was going to Cheltenham but in this adaptation, there is no Lily Marbury or Tom Hartigan, so she never came to the conclusion that Cust had lied.
In the NHK adaptation ABC Murders, Episode 5-8 of their anime series Agatha Christie's Great Detectives Poirot and Marple, Mrs Marbury is not told about Cheltenham either. Here, Cust tells Lily Marbury directly that he is going to Doncaster. Lily then asks her mother where Cust had gone on the days of the other murders and all the cities matched. So together they come to the conclusion that Cust might be the killer. But we are not told if they inform the police or not.