Tom and Leona Ogilvy arrive at the house that belonged to Tom's cousin Zachariah. They go in and find the house filled with antiques, and Tom explains that the Ogilvy's have been in the U.S. for three hundred years. The housekeeper, Miss Patience, finally comes from upstairs and says that she'll be leaving when the sun sets and tells them to hurry so she can show them around. As the couple goes upstairs, the doors behind them slam shut on their own.
Miss Patience takes them to the attic and shows them a trunk, and explains that she was the only one who stayed on after Zachariah drove everyone else away. Tom wants to set up the attic as a study, but Miss Patience warns that Zachariah didn't want the trunk to be moved, and claimed that someone would come to get it. The Ogilvy's decide to honor Zachariah's deathbed wish. After they leave, the trunk starts to shake on its own.
In the library, Leona admires a portrait of Zachariah while Tom discovers a number of books on the occult and raising the dead. Miss Patience ducks the question of Zachariah's interest in witchcraft, and the Ogilvys accompany her out. Her ride, Homer, refuses to come close to the house and Miss Patience explains that no one in the village will approach the house. Once she leaves, the couple goes to bed but neither one can sleep. They figure that Miss Patience was exaggerating about anyone approaching the house, but Tom notices that they are there. Outside the crickets chirp but then stop all at once.
The next day, Tom sets up his study in the attic. Leona returns and says that she looked up crickets. As Tom starts to work, the crickets stop chirping and he sees the trunk move on its own, swaying back and forth. Tom collapses over his typewriter, but then wakes up as the chirping starts again and the trunk stops moving.
That night, Tom is still working when he hears noises coming from the trunk. He walks over to it for a moment and then goes to the bedroom, waking up Leona. Leona says that he came to bed hours ago and then got back up and returned to the attic, and Tom doesn't believe it until he sees that his pillow has been slept on.
In the attic, the trunk opens and two goblin voices confer, saying that they cannot possess Leona because of her innocence. They boast that Tom's spirit is compliant, and invoke the Prince of Darkness to possess him. The trunk closes on its own and the typewriter starts typing out an invocation, speaking of how a hot white liquid poured by the Young Man onto the Young Woman's lips on the Sabbat-Day will cause them to forfeit their souls.
The next morning, Tom goes through Zachariah's books and snaps at Leona for making cheap oatmeal. He goes upstairs and finds the invocation on the typewriter, and accuses Leona of writing it. However, she has no idea what happened. He relents and wonders if kids on a dare snuck in. Spooked, Leona decides to move the trunk and calls in a mover from out of town to take it away. That night she hears Tom pacing in the attic and goes to see him. He tells her to go back to bed, but then sees that the trunk has reappeared in the attic. Tom hears Leona screaming and runs to the bedroom. She explains that a spirit was in bed with her and touched her.
The next day, Halloween, Tom seals the trunk up in a shed and goes inside. He asks for cocoa and Leona says that she ran out. Tom snaps at her and she argues back, and they start speaking in an older English style. Frustrated, Thomas snatches up the pan of hot milk and starts to pour it into her mouth, but snaps out of the spell as they realize that they almost completed the invocation from the typewriter. They hear a knock at the door and open it to find two spooks... children out for Halloween. The couple bursts into laughter and sends the children on their way, and then realizes that it's the one night of the year where spirits revisit their old haunts.
Tom runs to the attic and discovers that the trunk is still there. Meanwhile, there is another knock at the door. Leona opens it and finds Zachariah's corpse. He tells them that he's come for the trunk and walks up the stairs while the lights go out.
The next morning, the Ogilvy's realize that Zachariah wrote out the invocation on the typewriter to warn them until he could collect the trunk and the demons within on Halloween. Tom goes upstairs and finds a new trunk, with another message saying that someone will come for it. The note bursts into flames once they read it, and they realize that Zachariah will come in a year to get the trunk. They quickly put the house up for sale and drive away.