"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 who the Germans have taken captive to pry vital information about Englands military strategies...

"The following case has not previously been disclosed to the public due to the sensitive information on foreign affairs. All those involved were previously bound by the Official Secrets Act. With the passage of time and the onset of the Great War, these impediments have been removed and the story can now be safely told. When an executed original of a secret treaty between England and France, known as the French Treaty, is stolen from the country estate...

"In the west end of London, an apparently crazed individual is on the loose, breaking into art galleries and private homes to slash valuable paintings of women. Despite Scotland Yard's best efforts, the criminal remains at large and continues on his destructive path. When Joanna and the Watsons are called in to solve the mystery, they soon discover that although the canvases have been slashed, their backings remain pristine, with no cuts or scratches....