A crew of astronauts land on Mars and discover a mysterious object, which they take with them back to Earth. As they re-enter Earth's atmosphere, their shuttle begins to lose control and they crash shortly thereafter. The mysterious artifact is recovered from the wreckage. It isn't long before the aliens have seized control of Corridor 7. The aliens are in fact Martians, who vanished from Mars and became trapped in another dimension. Now they are free and are preparing to turn Earth into their new home.