"Sherlock Holmes' daughter faces a new unsolvable mystery with spies and a threat to the crown. Joanna and the Watsons receive an unexpected visitor to 221b Baker Street during a nocturnal storm. A rain-drenched Dr. Alexander Verner arrives with a most harrowing tale. Verner has just returned from an unsettling trip to see a patient who he believes is being held against his will. Joanna quickly realizes that Verner's patient is a high-ranking Englishman...