A normal, average guy who lives in New York City becomes dependent on an evil, disembodied brain.
Brian begins an unwilling symbiotic relationship with a malevolent leech-like brain-eating parasite called “Aylmer”. Aylmer secretes a highly addictive, hallucinogenic blue fluid into Brian’s brain. In return for a steady supply of the fluid, Brian must seek out human victims for Aylmer, so that he can devour their brains. All the while, though, as Brian adopts a heavily secluded life in his indulgence of Aylmer’s fluids, it begins to draw a rift in his relationship with his girlfriend Barbara and his brother.
The film climaxes with Brian being confronted by Morris and Martha; a middle aged couple who were Aylmer’s previous hosts before he escaped and found Brian. Holding Brian at gun point, they retrieve Aylmer from his back, Aylmer fights back and kills them both. But while Aylmer is feeding Brian his next dosage, Morris, who is still alive but only half thinking, fiercely grabs Aylmer and squeezes an overdose of his juice into Brian’s brain, causing him severe agony as it goes in to overload.
Aylmer dies and Morris succumbs to his injuries while Brian, still in agony from the overdose, retrieves Morris’s gun and shoots himself in the head. The movie concludes with a shot of Brian, not dead from the gunshot but now with a glowing hole in his head…