一帮雇佣兵偷走了匈奴王的预言宝剑，引发了一个古老的诅咒。所有神话中最恐怖的造物Cerberus将被唤醒。这只恐怖的三头犬有一条蜿蜒的尾巴，而且嗜血成性。

Will and Maura, despite their marital problems, decide to come to Ireland and live on Maura's ancestral estate, bringing with them their daughter Aubrey. But soon weird happenings around the house lead a local priest to confess that Maura's ancestors practiced black magic, and Maura's own insecurities threaten to bring her into the evil fold.