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".

A group of troopers take refuge in an abandoned outpost after fighting alien bugs, failing to realize that more danger lays in wait.

The war against the Bugs continues! A Federation Starship crash-lands on the distant Alien planet OM-1, stranding beloved leader Sky Marshal Anoke and several others, including comely but tough pilot Lola Beck. It's up to Colonel/General Johnny Rico, reluctant hero of the original Bug Invasion on Planet P, to lead a team of Troopers on a daring rescue mission.

The troopers of two starships have joined forces to terminate a massive bug attack at a Federation outpost. Before the mission can be completed and the survivors evacuated, one ship abruptly departs and goes inexplicably dark. The remaining battle-hardened troopers race to the rescue only to discover that the threat from the bugs is about to hit home.

Federation trooper Johnny Rico is ordered to work with a group of new recruits on a satellite station on Mars, where giant bugs have decided to target their next attack.