Mr. Keen, Tracer of Lost Persons - The Case of the Absent Minded Professor

Dr. Roland Barton, Professor of English Literature, is sitting with his wife Julia, in front of their fireplace. Julia looks sleepy, and the Dr. Barton asks her if she is feeling well. She said she is fine, just been having her usual trouble with indigestion. A minute or two later, Julia passes out in her chair. Dr. Barton calls for his stepdaughter, Joan Gardener. They soon discover that Julia has died.  A week later, Mr. Keen appears at the door of the Barton residence. Joan has called him to look into the matter. It seems that the night Julia died, someone has mixed a strong dose of sleeping powder in with her medicine for indigestion.