At a research station in Antarctica, scientists discovered a strange and ancient organism. They thought they could study it, classify it, control it. They couldn't. Six months ago, a secret paramilitary team called Unit 51 was sent to the station. They thought the creature was dead, the nightmare was over. It wasn't. In a Mexican temple, archeologists uncover the remains of a half-human hybrid. They believe it is related to the creature in Antarctica, a dark thing of legend that is still alive--and still evolving. They believe it needs a new host to feed, to mutate, to multiply. They're right. And they're next. And the human race might just be headed for extinction...