Shock

Janet Stewart arrives at the hotel hoping her husband Paul has already checked in, but he hasn't. The clerk can't locate her reservation and there are no open rooms, heightening her anxiety. She fears something might have happened to him, given he's been missing for two years.

She falls asleep on the hotel couch and has a hallucinatory dream in which Paul appears at the door, yet she cannot open it to let him in. He cries for help, leaving her waking distraught and confused. The dream blurs the line between fear and reality.

Waking, Janet follows a sound to the window and overhears a husband arguing with his wife about a divorce and a lover named Elaine. She sees the man in the next room’s window and witnesses him strike his wife with a candlestick. The scene leaves her horrified and shaken by what she has glimpsed.

The following morning Paul arrives hoping to surprise Janet, only to find her unresponsive. The hotel doctor diagnoses shock and recommends a specialist, suggesting Dr. Cross, who is staying at the hotel. Cross notes Janet’s proximity to his room could be dangerous and recommends she be taken to his private sanatorium instead.

At the sanatorium Cross hears Janet mutter what she saw and realizes she identified him as the killer. He explains that he didn't mean to kill his wife, but moved her body to a trunk and sent it to his lodge, leaving him unsure how to dodge manslaughter charges. He contemplates a plan with his lover Elaine to convince Janet she imagined the events.

Elaine pressures Cross to persuade Janet that she merely imagined the murder. Cross hesitates but ultimately agrees to go ahead with the plan, torn between exposure and self-preservation. The decision marks a dangerous turn as Janet’s grip on reality becomes a bargaining chip.

One night, disturbed inmate Mr. Edwards enters Janet's room and a struggle ensues with Elaine nearby. Janet panics, mistaking Edwards for Cross, and staff worry that her delusions will push her toward an official insanity declaration. Elaine warns that witnesses may seal her fate.

A few days later Mrs. Cross's body is found in a mountain ravine, initially ruled an accident. The case is reopened when a district attorney's investigator notes a possible pattern and orders a more thorough autopsy. Cross fears the new evidence could implicate him.

Mr. O'Neill from the district attorney's office visits Cross, reporting that a man has been arrested for breaking into a hotel near the mountain and beating a woman. He suggests this may fit a pattern that requires a deeper autopsy on Mrs. Cross's death. Cross contemplates using insulin as a way to uncover the truth from Janet.

Standing at a crossroads, Cross debates whether to perform an insulin shock treatment, even risking an overdose in the fourth dose. Elaine reminds him of their past tryst to pressure him into acting, but Cross ultimately declines for the moment. The ethical line between medical care and coercive manipulation becomes blurred.

O'Neill returns to tell Cross that the coroner has ruled Mrs. Cross's death a murder and that the weapon was a candlestick. Facing the truth, Cross feels he has no choice but to continue with the insulin plan to get a confession from Janet. The tension among investigators and staff tightens.

Paul visits Dr. Harvey to report Janet's insistence that she saw Cross kill his wife and to validate the insulin approach. Harvey notes that insulin treatment can reveal truth and they hurry toward the sanatorium to confront Cross and Janet. The alliance to uncover the facts accelerates.

Cross administers the fourth insulin dose, but as Janet struggles he orders dextrose to save her. Elaine refuses to provide it, and the struggle escalates until Cross strangulates her to avoid exposure. Harvey and Paul soon arrive to stabilize Janet and confront the unfolding danger.

Harvey administers adrenalin to revive Janet, who recovers quickly from the peril. Cross is arrested and taken away by O'Neill, his scheme exposed and thwarted for the moment. The hospital atmosphere settles into a fragile calm as the truth about the murders comes to light.