Using massive piloted robots to combat the alien threat, earth's survivors take the fight to the invading alien force lurking in the depths of the Pacific Ocean. Nearly defenseless in the face of the relentless enemy, the forces of mankind have no choice but to turn to two unlikely heroes who now stand as earth's final hope against the mounting apocalypse.

过去若有怪兽从环太平洋现身，都会有专为击退牠们而造的巨大机甲猎人奋力反抗。但好景不常，如今澳洲遭到怪兽肆虐，全洲人类被迫疏散。泰勒和海莉这对年幼的兄妹不幸走失，著急地寻找不见踪影的父母，过程中，两人学会操控一个废弃许久的破烂机甲猎人，因而有了突破眼前难关，杀出一线生机的希望。