Jack Caine (Dolph Lundgren) 饰演美国航天城休士顿的一个独立特行的副警官。当他正准备独自行动去破获一起毒品交易并想逮捕头号毒贩Victor Manning的时候,他卷入了一起秘密诱捕事件,他的搭档却被杀害了,他和FBI探员Lawrence Smith一道调查这一连串的神秘死亡现象,却发现有外星生物……Jack Caine (Dolph Lundgren) is a Houston vice cop who's forgotten the rule book. His self-appointed mission is to stop the drugs trade and the number one supplier Victor Manning. Whilst involved in an undercover operation to entrap Victor Manning, his partner gets killed, and a sinister newcomer enters the scene... Along with F.B.I. agent Lawrence Smith, the two investigate a spate of mysterious deaths; normal non-junkies dying of massive heroin overdoses and bearing the same horrific puncture marks on the forehead. This, coupled with Caine's own evidence, indicates an alien force is present on the streets of Houston, killing and gathering stocks of a rare drug found only in the brain... Caine is used to fighting the toughest of criminals, but up to now they've all been human...