 Irene Eaton (Sally Eilers) offers herself to secret service chief Shaw (Frank M. Thomas) for undercover work to find the saboteurs causing a rash of explosions, one of which killed her brother. She is accepted (despite having no experience), given a false identity and leads to a cafe, where she quickly learns who some of the underlings are and joins them. One appears to be James Huntley (Allan Lane), a photographer she picks up under orders of the chief underling (Fritz Leiber), after he swims ashore from an unknown vessel. But getting the "big boss" of it all is the object, and after many red herrings he is revealed at the end of the movie, which culminates at the uppermost floor of the Washington Monument.