The Secret Agent's Blunder

Mikhail Tulyev (Georgiy Zhzhonov), the son of a former spy and White Russian count, is sent by West German intelligence to collect Soviet nuclear secrets. He travels in Russia under the name Mikhail Zarokov, taken from a POW he had met in the Great Patriotic War, with the cover of looking for his supposedly lost sister. Tuylev stays with Dembovich (Oleg Zhakov), a bitter former German agent and works as a taxi driver, striking up a romantic relationship with the taxi company's dispatcher, Maria Nikolayevna (Eleonora Shashkova).

Through Dembovitch, Tuylev recruits an infamous thief known as "Snipe", who by chance, Tuylev had encountered during a train ride and is wanted for killing a prison guard during an escape attempt. However, "Snipe" is in actuality a KGB officer named Pavel Sinitsyn (Mikhail Nozhkin). Tuylev has Dembovitch order Sinitsyn steal soil and water samples from a nuclear testing site. Sinitsyn's superior, General Sergeyev (Yefim Kopelyan), having been informed of Tuylev's mission, orders Sinitsyn to fake his defection when he is to hand over the samples to Tuylev's contact, Leonid Krug (Vadim Zakharchenko), and subsequently act as a double agent. When the delivery happens, Pavel and Krug are attacked by a Maritime Border Troops ship. Despite Krug being shot in the leg, the two manage to escape to neutral waters.

After his successful escape with Krug into West Germany, Sinistyn is subjected to various attempted brainwashing techniques as Tuylev's superiors attempt to recruit him as an agent. Pavel is eventually accepted as an agent and sent to work as a sailor on a merchant vessel until he is called to action again. Elsewhere, Tuylev is forced to flee after a guilt-ridden Dembovich commits suicide and sends a letter to the KGB revealing Tuylev's identity and his complicity in the plot. After setting fire to Dembovitch's house, Tuylev, pursued by the KGB, switches cars, escapes, and manages to leave behind a considerable amount of money for Maria, who is pregnant with his child.

One year later, Sinistyn is ordered to return to the Soviet Union in order to resume contact with Tuylev, long since inactive and now living under the name Stanislav Kurnakov. Pavel is also asked to relay news of the death of Tuylev's father in Paris to him (In the following films, it is revealed that Tuylev's superiors orchestrated it with Tuylev's protégé Karl Brockman). After meeting with Tuylev, Sinistyn suggests to him that they go fishing the next morning. Tuylev obliges, and is apprehended by the KGB. As Tuylev is escorted away, Sergeyev then orders Sinistyn to adopt Tuylev's codename, "Hope" in order to fool his superiors to think Tuylev is still active.