Charles Condamine, a successful author, lives in Sussex with his second wife, Ruth. As the play opens, they are preparing for a dinner party. They have invited Dr Bradman, the local GP, Mrs Bradman and an eccentric clairvoyant, Madame Arcati.
Charles is working on a novel about a fraudulent medium, and has invited Arcati to conduct a séance for his research. It is clear before Madame Arcati arrives that the sceptical Condamines and Bradmans are treating the idea of a séance as a joke.
However, during the séance, strange knocks and manifestations suggest that something has indeed happened. When the guests leave, the ghost of Charles’ first wife Elvira materialises but only Charles can see or hear her.
Charles’ odd behaviour upsets Ruth, and the mood at breakfast the following morning is frosty. However, Charles succeeds in demonstrating to Ruth that Elvira is in the room. No love is lost between the two women, who can only converse via Charles. Ruth invites Madame Arcati to exorcise Elvira, and is upset to learn that it is beyond her powers.
Things come to a head when Ruth is killed in a car accident, engineered by Elvira in the hope of killing Charles so they can spend eternity together. A second séance only results in the ghost of Ruth being conjured up to join Elvira, and the two women work together to unsettle Charles.
Finally Madame Arcati returns and, after trances and incantations, proves that the ghosts have been summoned by another medium, the Condamine’s maid, Edith. Arcati succeeds in exorcising both the ghostly wives, and Charles escapes. As he leaves, he tells both the spirit wives his true feelings and they take revenge on him by unleashing supernatural phenomena which gradually destroy the house.