Callers for Dr. Morelle

In his Harley Street house, Dr. Morelle listens to Thelma Grayson describe how, the previous night, she had shot Ray Mercury. Thelma explains that Mercury had been responsible for her sister's suicide. The morning newspapers reported that Mercury had shot himself. Now, Thelma asks if she should give herself up to the police, or let them believe he shot himself? Morelle's search for the answer finds him and Miss Frayle adventuring into Soho's dark underworld, before finally trapping the murderer.