Art historian Kenji Kenmochi is married to the much younger Ikuko. Due to his waning virility, he has his doctor give him hormone injections. In addition, he tries to awaken the interest of his daughter Toshiko's fiancé, assistant doctor Kimura, in Ikuko, convinced that his jealousy will bring his manliness back. Ikuko agrees to the plan, as she has developed a genuine interest in Kimura. However, Kimura's main ambition for becoming part of the Kenmochi family is financing his continued studies with Kenji's money. Kenji eventually dies of a heart failure, an effect of his hormone injections.
After the funeral, Ikuko, Toshiko and Kimura plan to live together, although it isn't clear with which woman – or both – Kimura will be sleeping. As they begin their new life with a post-funeral meal, Toshiko tries to poison her mother's tea, not realizing that the poison insecticide powder had been switched with harmless household cleanser in their respective containers. As Toshiko awaits her mother's death from the poison tea, the family maid Hana poisons them all using the actual insecticide. Later the detectives read Ikuko's diary and, thereby discovering the incestuous love quadrangle, ascribe all three deaths to suicide, despite Hana's confession.
For the film, Ichikawa and his co-writers Natto Wada and Keiji Hasebe added a character not in the book, housemaid Hana, who in the finale (again not in the book) poisons Ikuko, Toshiko and Kimura.[5]
