Instead he is caught up in a battle against agents of "a certain foreign power", who have disguised themselves as negros and are in the process of eliminating all who they see as a threat. First to go are an airplane designer, a chemical research scientist, an international banker, a famous mechanical engineer, a U.S. Senator, and an undersecretary in the United States War Department. In some cases, unreliable witnesses had told of seeing a cloud of what looked like red snow descending on the area of these unfortunates. When the snow cleared, these victims had vanished completely! 

Doc and his assistants fight side-by-side with men of the U.S. Secret Service who have been trailing the group of European fanatics. The next target of the enemy's Red Snow device is the official train of the U.S. Secretary Of State. In a prelude to war, their battle fleet holds manuvers near the American coast, waiting for the signal to strike!