During a sweltering Fourth of July weekend, a sudden and powerful power failure blankets the mansion, and Olivia de Havilland as Cornelia Hilyard finds herself trapped between floors inside the elevator she insisted on installing—a rigid, cage-like contraption that becomes both her prison and her last thread to the outside world. With her son away for the holiday, William Swan as Malcolm Cornelius Hilyard, the house falls into a tense isolation, and Cornelia must navigate the claustrophobic metal enclosure with a growing sense of desperation and resolve.
Her only potential lifeline—the elevator’s emergency alarm—receives a chillingly indifferent response. The call lingers, and the person who finally answers is not a rescuer but the rough, unyielding figure of Jeff Corey as George L. Brady Jr., a desperate alcoholic who robs the home rather than saving it. Brady’s presence in this fortified mansion hints at a larger web of danger and crime that has quietly moved into the quiet suburb.
Brady’s opportunistic theft draws in a small-time fence, Charles Seel as Mr. Paul, who is eager to capitalize on the haul. Mr. Paul, in turn, enlists his hustler acquaintance, Ann Sothern as Sade, to help move the merchandise and keep the spoils out of sight. The promise of easy money brings three young hoodlums to the scene: James Caan as Randall Simpson O'Connell, Jennifer Billingsley as Elaine, and Rafael Campos as Essie. The intruders trail Brady and Sade back to the mansion, drawn by the glittering array of valuables that now sits at the heart of Cornelia’s isolated world.
Cornelia pleads with them for mercy, offering to let them take whatever they want and promising not to involve the police if they release her. Instead of gratitude, the thieves turn contemptuous, ransacking the house and quickly becoming intoxicated on the liquor they find. The situation spirals into a brutal, unhinged scene as the intruders revel in their power, culminating in a savage act that shatters the night: Brady is killed, and Sade is locked away in a closet as the others continue their raid.
Randall crawls up to the elevator and taunts Cornelia, insinuating a disturbing indictment about Malcolm’s sexuality, while displaying a letter Malcolm left that very morning on her nightstand. In the letter, the son reveals his torment and hints at suicidal thoughts provoked by his mother’s domineering grip. The revelation leaves Cornelia stunned and fainting, the weight of the accusation pressing down on her in the claustrophobic gloom of the cage.
With the thieves preoccupied by their own greed, Paul and his men arrive to reap the stolen goods from the hoodlums’ car, intensifying the danger inside the mansion. When Cornelia regains consciousness, she refuses to surrender, and in a moment of desperation she rips the elevator’s door apart and improvises makeshift shivs from the broken metal. She injures herself in the process but manages to crawl toward the front door, only to be dragged back inside by Randall.
In a pivotal moment of courage and fury, Cornelia uses the improvised tools to stab Randall in the eyes, a brutal act that leaves him disoriented and blinded within the living room. The violence, combined with the cumulative stress of the ordeal, pushes Cornelia toward a fragile edge of sanity, a temporary insanity that leaves her dazed and overwhelmed by what she has just done.
As the thieves begin to retreat, Cornelia, still reeling, mistakes Essie for Malcolm and speaks in a tremulous, remorseful voice about the man she believes she has harmed. She crawls back toward the front door, a frail figure struggling to regain control of her own home. Randall, still pursued by guilt and fate, stumbles onto the road and is fatally struck by a passing car, drawing a crowd of witnesses who rush to help the injured woman.
The arrival of the police brings a fragile moment of relief, even as the criminals try to flee. Essie and Elaine attempt to escape in a car, but their plan is thwarted when they crash into the mansion’s electric box, inadvertently restarting the power. The house’s elevator lurches downward to the floor, its doors opening to reveal the evidence of the night’s chaos. Essie and Elaine are arrested, while the survivors—Cornelia and the others—receive a quiet, uneasy comfort as they begin to reckon with the consequences of the night’s violence.
