The plot is set in motion when a woman named Mrs. Warren seeks the help of the brilliant consulting detective Sherlock Holmes. Ten days earlier, Mrs. Warren rented a room to a young man. She has not seen her lodger since that day, although she hears him walking around in his room constantly. She is worried that there is some reason why the man has gone into hiding. Although the case at first appears to be trivial, Holmes soon discovers that it is connected to serious crime. The story has been adapted for radio and television.