Ilija Čvorović (Danilo Stojković), a former Stalinist who spent several years in a prison on Goli otok, is contacted by the police to routinely answer questions about his sub-tenant, Petar Markov Jakovljević (Bora Todorović), a businessman, who spent twenty years living in Paris, and now has returned to Belgrade to open a tailor shop. After only several minutes, Ilija is free to go, however, he starts to suspect that his sub-tenant, Petar, might be a spy. As time passes, Ilija becomes convinced that Petar, a modern man from a capitalist country, represents a great threat to national security and the socialist system, and begins spying on Petar. Ilija's wife Danica (Mira Banjac) is more concerned with the future of their daughter Sonja (Sonja Savić), who, although holding a degree in dentistry, is unable to find a job. After a bout of spying, Ilija phones inspector Dražić (Milan Štrljić), claiming that Petar was meeting with "suspicious people" (actually Petar's intellectual friends), but Dražić does not take him seriously. Ilija decides to take matters into his own hands. He begins his own surveillance operation against the innocent man and his friends. Eventually, he bars his house, buys a guard dog, arms himself with munition, and even gets help from his brother Đura (Zvonko Lepetić), both of them becoming convinced that Petar is a foreign agent.