Richard Clark, Donald Grant, a struggling reporter at a San Francisco news agency, learns of a string of closet murders through his snarky rival Scoop Johnson, [Frank Ashmore]. Hoping for a breakthrough, he heads to the small town of Chestnut Hills to uncover who is behind the killings. There he meets Diane Bennett, [Denise DuBarry], a local biology teacher, and her young son, Professor Bennett, [Paul Walker].
Together with Sheriff Sam Ketchem, [Claude Akins], they begin to investigate the first crime scene—a sorority house where a woman’s husband is slaughtered by a creature lurking in a closet. A terrified neighbor witnesses the attack and Richard discovers a large, clawed fragment on the ground near the victim’s body. The evidence points toward something otherworldly, something that refuses to be stopped by ordinary gunfire.
Diane Bennett brings the strange fingernail to Dr. Philip Pennyworth, [Henry Gibson], who becomes deeply involved in the search for answers. That night, Richard returns to Diane’s home for dinner with Dr. Pennyworth and Father Martin Finnegan, [Howard Duff], and they are interrupted by a neighbour’s panicked screams. A monster emerges, scales shining and claws flashing, slaughtering Sheriff Ketchem as the police watch in shock. The creature proves nearly invulnerable to bullets, and the town quickly springs into lockdown as military forces take charge.
The military presence brings a plan to communicate with the monster through sound, with Pennyworth suggesting a glockenspiel might do the trick. Richard, Diane, Father Finnegan, and Pennyworth set out to locate the monster, later joined by Scoop Johnson. A confrontation with a soldier leads to a tense stand-off, and General Turnbull, [Donald Moffat], confronts them about their role in the crisis. When it becomes clear that the monster is converging on the local elementary school because Professor Bennett is there, the group races to save the child and narrowly succeeds just in time.
Despite orders to contain the creature, Pennyworth is determined to study it alive and charges toward the monster, only to be killed. The army returns, but the monster survives the assault and bolts into the surrounding chaos, forcing the remaining townspeople to abandon Chestnut Hills. Diane realizes that electricity might be the key to defeating the beast, having learned from Pennyworth that the claw’s electrons could be its weakness. She and Richard improvise a trap using scrap metal and electric wires, but the monster tears it apart and the two flee into the attic, hoping for a last-minute survival.
As their energy drains, the monster sights Richard’s face and, captivated, lifts him out of the attic and into the open air. In a desperate bid to stop the creature, Diane appears on live television and urges everyone to destroy their closets to deprive the monster of renewed power. The threat shifts to San Francisco, where the creature carries Richard to the Transamerica Pyramid, seeking the only closet that remains intact. Unable to fit, the monster finally runs out of energy and collapses, dying amid the stunned crowd.
In the aftermath, the residents evacuate as the news coverage continues. A reporter’s quip about the closets’ role is met with Father Finnegan’s calm, ironic reply: > Oh, no. It wasn't the closet. It was Beauty killed the Beast.
