In the novella Murder in the Mews, Mrs Barbara Allen (née Armitage) was a young woman of about twenty seven years of age. When her dead body was discovered in her bedroom, it first appeared to be a case of suicide. However the police doctor Brett noticed something unusual in the arrangement of the body. The gun, which belonged to her, was in the curve of her right hand. It looked like she was holding it but in fact she wasn't holding it. Moreover, the bullet wound was above the left ear and it was impossible to inflict such a wound on herself holding the gun in her right hand. It appeared that someone had murdered her and had clumsily made it appear as a suicide.
Barbara's maiden name was Armitage. She had apparently married to someone and had a child who died at the age of three. At the time of Barbara's death, she was engaged to an M.P. Charles Laverton-West.
Mrs Barbara Allen did appear in the film adaptation of the story as part of ITV's Agatha Christie's Poirot drama series. However she is seen only as a dead body is shown as well as in a photo of her taken by her friend Jane Plenderleith. The actress who portrayed Barbara Allen is not credited.