A woman goes on vacation with her family and friends and her husband and her daughter encounters a tragic accident. One year later she goes hiking with her friends and they get trapped in the cave. With a lack of supply, they struggle to survive and they meet strange blood thirsty creatures.　　六个女孩相约进行一个探险旅行，她们来到一个深不可测的岩洞中，然而就在她们进入洞中不久后，突然爆发的崩塌封住了山洞的入口，让她们断绝了和外界的联系，六个女孩在无边而未知的黑暗中开始寻找生机，但是很快，她们就意识到，在这个不知道多少万年前形成的古老岩洞里，她们并不是唯一的生物……