Years after an alien invasion almost extinguished human mankind, refugee on a secret base on the Moon, three heroes decide to jump into a time travel in the desperate attempt to save the survivors but they don't know that the Sentinel is waiting for them.

几年前，一场外星人入侵几乎消灭了月球秘密基地的难民人类，三位英雄决定加入时间旅行，不顾一切地试图拯救幸存者，但他们不知道哨兵在等着他们。