One evening Nurse Helen Chester is asked to prepare the corpse of an old lady (who was a medium) for her funeral. While doing so, she is attracted by the elderly woman's diamond ring. As she steals it, a glass tips over (drops of water begin to splash on the ground) and she is also assailed by a fly smelling the dead body .
Once she is back home,she doesn't feel at ease because strange events begin to occur : another fly annoys her (or is it the very same one ?), the lights go out, the sound of dripping water comes from every room of her appartment, and she is plagued by threatening visions of the old lady.
Terrified, the nurse begs for forgiveness, and she strangles herself while thinking that it is the medium who is doing so.
The following morning, Helen's downstairs neighbour (or her concierge, that is not very clear or water-clear shall I say...) discovers her body. While the police inspectors examinate the place, the neighbour seems to be terrified by a simple fly...