Zack Mayo is an aloof, taciturn man who aspires to be a navy pilot. Once he arrives at training camp for his 13-week officer's course, Mayo runs afoul of abrasive, no-nonsense drill Sergeant Emil Foley. Mayo is an excellent cadet, but a little cold around the heart, so Foley rides him mercilessly, sensing that the young man would be prime officer material if he weren't so self-involved. Zack's affair with a working girl is likewise compromised by his unwillingness to give of himself.

After witnessing a man's death in a bizzare accident, Father Pergado goes on a spiritual retreat, where he encounters his alien double bent on world conquest.