Alan Grant, Scotland Yard Inspector (a character who also appears in five other novels by the same author) is feeling bored while confined to bed in hospital with a broken leg. Marta Hallard, an actress friend of his, suggests that he should amuse himself by researching a historical mystery. She brings him some pictures of historical characters, aware of Grant's interest in human faces.
He becomes intrigued by a portrait of King Richard III. He prides himself on being able to read a person's character from his appearance, and King Richard seems to him a gentle and kind and wise man. Why is everyone so sure that he was a cruel murderer?
With the help of other friends and acquaintances, Grant investigates Richard's life and the case of the Princes in the Tower, testing out his theories on the doctors and nurses who attend to him. Grant spends weeks pondering historical information and documents with the help of Brent Carradine, a likeable young American researcher working in the British Museum. Using his detective's logic, he comes to the conclusion that the claim of Richard being a murderer is a fabrication of Tudor propaganda, as is the popular image of the King as a monstrous hunchback.