The spaceman's ship is attacked by aliens. He flees through a wormhole and crash lands on a planet covered in metal. He finds a space dock inhabited by humans but under attack by evolved aliens. The spaceman uses a defense turret to destroy an alien ship. He later salvages an alien battle pod and upgrades it to scout and attack the aliens, but they are too numerous. To save the future, the spaceman travels back through the wormhole and destroys the aliens' home planet, but causes a paradox that threatens to destroy the past and future.