Years after an alien invasion nearly extinguished the human race, three soldiers who survived on a secret moon base are sent to Earth to liberate the survivors from the Sentinel and its army and reclaim Earth at any cost.

An asteroid shower lands in a remote section of the Grand Canyon and begins to spread mysterious pods. Meanwhile, scientists on a space station that has been hit by the same asteroid shower, discover that a pod has mutated into a creature and is threatening the ship. Now the scientists and a team on Earth must learn to defeat this alien force, fighting fire with fire, fighting stone with stone.