Miss Elspeth Brownrigg, an elderly spinster who devotes her money and her life to an orphanage, receives a letter threatening her with death unless she is willing to pay GBP5,000 within 48 hours. When she has raised the money, she is to place a plain postcard in her window. She calls in her nephew, Norman Brownrigg, who is a member of Scotland Yard. His superior, Detective Inspector Evans, accompanies him to investigate the case. Slight suspicion attaches itself to Sydney Martin, Miss Brownrigg's secretary. However, the investigators determine to place the card in the window and await developments. A further communication tells Miss Brownrigg that she is to make a parcel of the money and go to the bargain basement of a large department store. She takes a dummy package and her bag is snatched in the crowd. She receives a last warning-unless she pays by 11.00 p.m. the threat will be fulfilled. It is signed like the previous notes by a pair of black wings. Inspector Evans, Norman Brownrigg, Sydney Martin, and Elsa Waring, a young friend of Miss Brownrigg, agree to spend the evening with her to see that no harm befalls her. The fatal hour strikes, nothing has happened. Miss Brownrigg suggests refreshments. She takes one sip of her coffee and the next instant crashes forward into her nephew's arms.