Colonel Johnny Rico finds himself battling bugs, new and old, on the Federation frontier planet known as Roku San.
Off-duty, Rico and his old friend Dix Hauser get into a bar-fight with farmers protesting the war. During the fight, Rico strikes Dix to stop him from shooting one of the farmers. Dix arrests him but the base is attacked by Arachnids and Rico is needed for its defense. When Roku San falls, Rico is blamed by the Federal Media and set for execution for insubordination and striking a superior officer. But the Federation has other plans for him. Captain Lola Beck is marooned on a classified planet known as Planet OM-1 with Sky Marshall Anoke.
Rico must lead the Marauders, an elite team of troopers, on a rescue mission, using the Federation's new battle-suits. Rico and the Marauders defeat the Arachnids on OM-1, and save their fellow soldiers from death at the hands of a treasonous element operating within Federation itself. OM-1 is discovered to be the home of the Bug Hive, the Arachnid's ruling body, and is destroyed by a "Q-Bomb." Rico is subsequently promoted to general, and given permanent command of the Marauder program.