Dr. Alexander 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 Alistair Ainsworth, a high-ranking cryptographer who the Germans have taken captive to pry vital information about England's military strategies for the Great War. Ainsworth must be found at all costs-- and Joanna and the Watsons might be the only ones who can connect the clues...