An evil scientist implants the brain of a murdered high school student into an animatronic Tyrannosaurus, who later wreaks vengeance on the bullies who killed him, and is reunited with his sweetheart.

Set in the future, the story follows a young soldier named Johnny Rico and his exploits in the Mobile Infantry. Rico's military career progresses from recruit to non-commissioned officer and finally to officer against the backdrop of an interstellar war between mankind and an arachnoid species known as "the Bugs".