After the suicide of Victor Darnley's wife in a locked attic room, the Darnley house and especially said room became to be known as haunted and none of its tenants stayed for long. But when mediumistic Alice Latimer and her husband Patrick move in, things take a sudden turn. Alice suspects that Victor's wife had actually been murdered in that locked room and that the footsteps and noises at night symbolize her spirit's manifestation and the wish to expose her murderer. Consequently an experiment is planned in the attic: Patrick will stay in the haunted room to confirm Mrs. Darnley's manifestation and the door will be sealed with wax and a rare coin while somebody knocks on the door every half an hour to see whether Patrick answers and everything is fine. When Patrick ceases to answer and the seal is removed, Patrick is not in the room and instead the corpse of another person lies on the floor!
