At a railway station cafe, housewife Laura Jesson meets doctor Alec Harvey. Both of them are already married, but they continue to meet at the cafe every Thursday despite the knowledge that their blossoming love is impossible.

An English mystery novelist invites a medium over for dinner in the hopes of gathering enough material for his latest book, as well as exposing her as a charlatan. However, a series of incidents occur during the course of the evening, which result in a chain of supernatural events being set in motion which wreak havoc on his present marriage.