Scientists investigate a huge meteor that crashes into the ocean off Mexico, and encounter a skyscraper-tall, mobile machine which is designed to syphon energy from earth, including any energy directed at it in an effort to destroy it.

A scrappy fighter from Jersey City named Tommy Shea -- "born in a dump, educated in an alley" -- catches the eye of wealthy businessman, Robert Mallinson, who allows him to train at his Long Island estate. Shea soon falls for Mallinson's daughter, Dorothy, but fears he doesn't have the money to support her in proper style. To get this money, Shea decides to work with crooked fight-promoter Harry Cram, even though this means dropping his honest manager, Dave Bernstein. As the big fight approaches, however, Shea begins to have second thoughts.

Aliens have landed and are hiding on Earth, but need Earth’s scientists to help them fight an inter-planetary war.