Earth is a desolate wasteland, humanity has been decimated by an invasion of Phantoms, insubstantial aliens that extract and devour the spirits of living things. The few remaining humans have retreated to a handful of cities that are protected by massive bio-energy shields. The beautiful Dr. Aki Ross and her mentor Dr. Sid have discovered that the energy signatures of eight key Earth spirits can cancel out and destroy the Phantoms. With the help of Captain Edwards and his band of marines, they must scour the globe for the last two remaining spirits before General Hein manipulates the refugee government into attacking the aliens with an orbital laser that may also destroy the Earth.