The film begins in the year 1996 (year zero). A group of infants are chosen by a commander to be raised as soldiers. One of the infants chosen is Todd. As Todd grows, he undergoes extreme mental and physical training to prepare for his career as a soldier. This includes phrase repetition conditioning, running, weapons training, wrestling, boxing and desensitization to violence. As time goes on, and he endures his training, Todd appears to be one of the best in his group.
The film then jumps to 2036 (year forty). Todd is now forty years old, and is shown to be a veteran of many battles. Eventually, a commander announces that he intends to replace Todd and the others with a new group of genetically-engineered soldiers. The commander makes it clear that the new soldiers are superior in strength and ability, making the ones trained from birth obsolete.
Refusing this idea, Todd's own commander suggests that his group are not obsolete, and are in fact are the best. The two commanders run their respective units through several tests designed to determine the better soldiers. As part of the testing regimen, a handful of the "human" soldiers engage in brutal hand-to-hand combat with the new group. Todd's group is no match for the genetically-engineered soldiers; several members of his unit are killed. Todd badly damages Caine (Lee), but is finally knocked unconscious and believed dead. Todd and the dead bodies are transported to a waste disposal planet known as Arcadia, where they are dumped onto the planet along with the trash. The surviving members of Todd's group are remanded to medial support roles and stripped of the title 'Soldier'.
As the disposal ship approaches Arcadia, Todd wakes up, lying amongst trash and his dead comrades. He realizes where he is just as the bottom doors of the ship are opened a few feet above the surface, dumping him and the debris onto the surface. Recovering, Todd begins walking along the surface. Eventually, he runs across a group of fellow humans, who left Earth twelve years earlier in 2024, only to crash-land on Arcadia. They live as a closely-knit community among the planet's trash heaps.
Overcoming the initial apprehension of some of the settlers, Todd wins acceptance into their community. He begins a new life with them, albeit with difficulty because of his combat-focused mental conditioning. He continues to exhibit a stern, tough behavior, despite the settlers' attempts to integrate him into their lifestyle. He is, however, able to make friends with a settler named Mace, and teaches Mace's son survival skills, such as the best way to kill a snake. During a flashback, Todd mistakes one of their number for an enemy, and nearly kills him. As a result, the settlers decide to send him into exile. They provide him with supplies and send him on his way, Mace wishing him luck as he leaves. Todd settles in an old drainpipe among the garbage heaps of the planet. It is there that his emotions finally overcome him, and he sheds a tear due to his failure to adapt to the colonist's society.