西元709年，外星人凯坦（James Caviezel 饰）驾驶的飞船坠毁在挪威境内，同伴重伤死亡，飞船损毁，沉入湖底。凯坦凭借随身携带的先进机器掌握了地球的知识和当地的语言，在森林内游荡之际，他遇到了维京人乌弗里克（Jack Huston 杰克•休斯顿 饰），并随之回到了村庄。 　　凯坦告诉维京人自己正在寻找一头“恶龙”，而这条恶龙正是他飞船上的一只怪兽，因飞船坠毁逃遁。维京人起初认为凯坦是个说大话的骗子，但随着村民一个个离奇消失，他们才发现所谓的“恶龙”真的存在……In 709 AD, in the Iron Age, a spacecraft crashes in the Viking kingdom of Herot, Norway, and the pilot Kainan survives. He turns the beacon on; learns the language and culture of the planet using a machine; and finds that the predator, Moorwen, that he was transporting, had escaped. While chasing the alien monster, he finds a village completely destroyed and is arrested by the warrior Wulfric, believing that he killed the locals - Kainan is brought to Herot as a prisoner.