An Italian submarine commander manages to sink an English warship and take its very British commander as prisoner. The film is based on the relationship which develops between the two characters.

Dr. Fred Steele (Umberto Orsini) and Eve Barnett (Maya Brent) work together at an astronomical station on a bucolic island. The station's scientists learn they must deal with a rogue planet -- "The Outsider" -- that has entered the solar system. which must be controlled by an alien intelligence… Professor Benson's(Claude Rains) expedition discovers a race of humanoid creatures dead...