The Red Thumb Mark
Dr John Thorndyke assisted by his friend Dr Jervis are called on to defend a young man, Reuben Hornby. Reuben is arrested for the theft of diamonds from his uncle's safe when a red thumb print is found in the safe matching Reuben's left thumb. With the police positive they've got their man, can Thorndyke use forensic science to save this innocent man from jail?