A string of murders leads Inspector McCormick of Scotland Yard to believe that a serial killer is loose in London. Only a few facts remain to be cleared up; such as how the murderer is getting to his victims, and how to catch him. But when their lead suspect turns out to be the harmless-but-eccentric reporter, Jeffry Floyd, an unlikely alliance is formed. Floyd reveals that the supervillains are also being picked off one at a time, and he intends to find out who is responsible. But matters are complicated when Sergeant Adams' sister comes to town. Kate Adams is nothing at all like her brother, and manages to get thoroughly mixed up in the double murder investigation, the supervillain underworld, and--unexpectedly--the life of Jeffry Floyd.