Police lieutenant detective Thomas 'Thom' Randall's steady girl-friend, Dr. Jennifer 'Jen' Allen, is Dr. Aaron Michaels's main assistant on his pharmaceutical firm Bellion's research program to cure the highly contagious, fatal infection Guinin. A convicted murderer, whom Thom arrested, is one of their special drug test subjects, but escapes. The convict and Jen are affected by radioactively altered DNA from an experimental reactor used on mosquitoes which transfer quinine. The convict soon mutates into a mosquito-like monster, which sucks its victims dry. By the time Thom and his junior murder brigade partner Charlie Morrison figure out what happens, Jen starts mutating herself. 一位科学家试图研制出一种能够对付West Nile病毒的疫苗，并用死刑犯进行试验。不料其中一个犯人在试验室突然狂性大发，他突变为半人半蚊的怪物并且开始寻找新成员。至于这位科学家女士，她也受到了同样的感染，只是突变较为缓慢而已。所以她必须和时间赛跑，尽早杀死蚊人并且找到治愈的方法。这时这位美女科学家即将完成变化，蚊人企图将她带走进行交配，但她最后的理性帮助她用电击干掉蚊人但自己也牺牲了！
