In Los Angeles, a bio-engineered creature called a Syngenor (SYNthesized GENetic ORganism) hides in the city’s sewers, slipping onto the streets at night in search of human spinal fluid. The police are stymied by the lack of eyewitnesses and fingerprints, and the news media ridicules them as the body count grows, with brutal feats like ripping doors off cars and pulling a victim’s hair hard enough to snap a neck. Ted Lonergan is a former detective turned novelist who is repeatedly urged by his former partner, Detective Lou Capell, to weigh in on the case, but he refuses, focusing instead on pursuing Jennifer Stanton after a chance collision where he backs into her car.
When [Jennifer Stanton] is attacked and left in a coma, Ted experiences a turn of heart. A young woman named Sherry Carpenter comes forward with a crucial lead: Jennifer’s spinal fluid may have been drained by a Syngenor created at a laboratory where she worked. Its creator, Dr. Ed Amberdine, had worked on the project alone, and after his death no one continued to monitor it. Sherry explains that the Syngenor’s attacks often present as a brain tumor, a detail that has kept the official counts alarmingly low. The police chief, Police Chief Dennis Warren, tries to control the narrative by identifying a man killed in a shootout as the killer, hoping to end the media embarrassment.
Ted and Sherry push farther, heading to the laboratory to retrieve Amberdine’s notes, where they discover a half-dead sewer maintenance worker—evidence of the creature’s secret pipeline. Realizing the sewer passages are the Syngenor’s primary route for movement and concealment, they descend into the underground and uncover the lair. Inside, they find a shocking sight: multiple unconscious humans connected to embryonic Syngenors by feeding tubes—the progeny produced by the original creature. Ted shoots the embryos, and the noise draws the adult Syngenor, which proves to be bulletproof.
A tense escape leads them to a rusting metal workshop, where every exit is locked. Ted decides to lure the Syngenor onto a heavy drop forge instead of fleeing. The creature closes in, attempting to drain his spinal fluid once more. Lou arrives and shoots the creature, driving it back toward the forge. In a final, desperate move, Sherry activates the machine, and the forge crushes the Syngenor. Jennifer awakens from her coma, but the ordeal leaves her with hysteria and fearsome, lingering hallucinations.
