In the future, humanity is embroiled in an ongoing war against a race of insect-like aliens known as the Arachnids or "Bugs". Johnny Rico, once again a Mobile Infantry soldier, has been demoted and sent to command a remote outpost on a planet far from the front lines. After his base is attacked by the bugs, Rico is falsely accused of failing to perform his duty and is sentenced to death. Meanwhile, the Federation launches a secret mission to capture a "brain bug" to turn the tide of the war, complicating the political landscape as faith in the military's ability to win begins to wane.

Before Rico's execution can be carried out, his old friend and pilot, Lola Beck, crashes on a remote planet infested with bugs. With the possibility of a high-level rescue mission dwindling, he is offered a chance for redemption and to prove his loyalty to the Federation. Rico embarks on a daring mission to save not only Beck but also his own reputation. Armed with a new, powerful suit of armor and leading a rugged team of soldiers equipped with the same, Rico faces off against overwhelming odds in a desperate bid for survival and to rescue his comrades from a fate worse than death.