It is set in 1930s Helsinki and centers on Inspector Palmu's investigation of the murder of rich and decadent Bruno Rygseck.

The film opens with a scene of guests arriving at the crime-themed dinner party of Bruno Rygseck, the rich and decadent heir of the Rykämö concern.

The next morning, inspector Frans J. Palmu and detectives Virta and Kokki are informed that Bruno has drowned in his indoor swimming pool after slipping on a bar of soap.

The atmosphere in the house becomes increasingly hostile towards the investigation as Palmu asks more detailed questions about the morning's events.

He learns that the previous night, Aimo had stolen Amalia's cat and brought it with him to the dinner party, where Bruno had poisoned it and invited her to view the cadaver for his amusement.

Despite Palmu's suspicions, the investigation is closed due to pressure from the powerful Rygsecks and because there is no evidence to prove that the death was anything other than an accident.

When Palmu and the detectives arrive back at the police station late in the afternoon, they are told that Alli Rygseck has been poisoned with prussic acid mixed in her absinthe.

Palmu interrogates Airi about the promissory notes, and she reveals that Aimo had been forging Bruno's signature to pay off his gambling debts.

In Bruno's bedroom, Palmu finds an album of nude photographs he had taken of his female friends, with one page torn off.

That evening, the policemen meet Bruno's uncle Gunnar Rygseck, the head of the Rykämö concern, at his office.

Palmu goes to interrogate Vanne again, and she confesses to having secretly stayed in Alli Rygseck's old bedroom on the night of the party.

In the final scene, it is revealed that Amalia has been mentally ill for some time and that she murdered Bruno as revenge for killing her cat.