Night Watch

During a raging thunderstorm in London, Ellen frantically reports to John that she saw a man with his throat slit in the deserted house across the street. John calls the police, but a thorough search finds no evidence of a murder.

The next morning, Ellen spots a freshly planted bed of Laburnum in the garden near the old house that wasn't there before. She suspects the absence of a crime scene and informs Inspector Walker, pushing for a dig.

Inspector Walker questions neighbour Mr. Appleby, who confirms he planted the trees during the stormy night. He refuses to let police search the garden or dig up the trees.

Ellen is still recovering from a nervous breakdown triggered by her late husband Carl's death in a car accident and from recurring nightmares. Her memory of the events is unsettled and she clings to the murder rumor.

That night, Ellen and her friend Sarah see a light moving behind the old house's shutters, prompting the police to search. They find Mr. Appleby wandering with a flashlight and arrest him for trespassing.

A second search of the house and the garden yields no evidence of a crime. Inspector Walker privately informs John that the case is officially closed.

That evening, Ellen asserts to John and Sarah that she saw another body in the old house, this time a woman. The claim raises tension and worry among them.

Believing she may be losing her mind, John and Sarah sedate Ellen. She agrees to see Tony, a psychiatrist friend who may interpret her memories.

In therapy, Tony has Ellen recount Carl's fatal crash. He recommends a clinic in Switzerland for a few weeks to stabilize her, and Ellen agrees to go.

Ellen calls Inspector Walker to search the old house again. He promises to look but then reveals that the house was purchased six months earlier by a private company called DIPCO.

As she prepares to depart for Switzerland, John asks Ellen to sign financial documents, including power of attorney. She notices he has acquired DIPCO and suspects a deeper plot involving their affair.

Ellen confronts John and Sarah and lures them to the old house's second-floor room. There, she slashes John's throat and stabs Sarah to death, then positions them in exactly the same manner she claimed to have seen.

It is revealed that Ellen had feigned insanity to carry out the murders as part of an elaborate scheme to tire the police and eliminate John and Sarah. The ruse explains her earlier sightings and calls as calculated steps.

Mr. Appleby visits, congratulates Ellen on pulling off the scheme, and says he won't report the murders. Ellen asks him to look after her house and the garden before she departs for Switzerland.