A slaughterhouse worker, Antti Rahikainen [Markku Toikka], murders a man. The lone witness is a catering-service worker, Eeva Laakso [Aino Seppo], who chooses not to call the police, instead telling him to leave. As the investigation unfolds, Rahikainen wanders through Helsinki, skipping his shift and noticing a newspaper article about the crime. A coworker urges him to take the week off, while Rahikainen quietly pursues a dangerous plan.
Rahikainen tracks down Eeva and asks her to meet after her shift, insisting she remember the words Silver Lining Hostel. He returns home to find a subpoena ordering him to appear for the murder, and the next day at the police station he is questioned about where he was at the time of the crime and his connection to Kari Honkanen [Pentti Auer], a businessman who had been killed. It is revealed that three years earlier Rahikainen’s fiancée was killed by Honkanen in a drink-driving crash, and when the court did not charge Honkanen, Rahikainen swore to take revenge.
Eeva returns to the station and, once again, refuses to identify Rahikainen, forcing the police to release him. The two eventually meet on a night ferry, where Rahikainen explains that he killed Honkanen because he “found him disgusting” and “wanted to show that things are less simple than people think.” As Rahikainen starts to abandon his job and plot a possible escape abroad, he and Eeva grow closer. She discovers the gun at his apartment and pockets it, while a man pursuing them, Heinonen [Hannu Lauri], who has been watching through the walls, tries to pressure Eeva into accepting his marriage proposal. She manages to escape by threatening him with the gun.
When Heinonen goes to confront Rahikainen, he is struck by a tram and dies. Inspector Pennanen [Esko Nikkari] remains suspicious, but a different man ultimately confesses and is charged, allowing Rahikainen to avoid immediate detention. Guilt gnaws at him as the days pass, and he contemplates his uncertain future. With a fake passport in hand, Rahikainen and a friend prepare to board a night ferry to Stockholm, yet a final glance at Eeva convinces him to turn himself in at the police station.
The verdict comes: eight years in prison. While inside, Rahikainen confides in Eeva, explaining the moral weight of his choices and the cost of revenge. In a farewell that echoes his earlier confession, he tells her the line that closes his arc: > I killed a louse and I became a louse myself.
