A phony psychic tries to solve a murder that took place during her seance.

A Parisian sewer worker longs for a rise in status and a beautiful wife. He rescues a girl from the police, lives with her in a barren flat on the seventh floor, and then marches away to war.

The story is told in flashback. Backers want a gambler to marry a rich girl for her dowry.

Betrayal and espionage abound as an experimental aircraft is readied for its maiden voyage.