Charles and Kate are summoned to Scotland on a mysterious errand for the Crown. Upon their arrival, they discover they will be staying at Glamis Castle, the most historic castle in Scotland, a place haunted by shadows and dark secrets. They learn that Prince Eddy, who had been heir to the throne until his supposed death in 1892, is still alive, ten years later. Only now the prince has gone missing - on the very morning that the body of one of his servants was found, her throat slashed. Now, Charles and his clever Kate must find Eddy and clear him from suspicion of murder, while keeping his true identity a secret.