A man wakes up in a pit of dead bodies with no memory of who he is or how he got there. Fleeing the scene, he breaks into a nearby house and is met at gunpoint by a group of terrified strangers, all suffering from memory loss. Suspicion gives way to violence as the group starts to piece together clues about their identities, but when they uncover a threat that's more vicious - and hungry - than each other, they are forced to figure out what brought them all together - before it's too late.

In the early 70's, Commander Nathan Walker, Captain Ben Anderson and Lieutenant Colonel John Grey are assigned in a secret mission to the Moon to protect the USA from USSR using detectors. Nathan and Ben land on the Moon in the Liberty module while John stays in orbit in the module Freedom. They collect rock samples and bring them to the Liberty. They also find footprints and the body of a Soviet cosmonaut on the moon. Soon they hear weird noises and they find that they are not alone in the satellite.