Once in the city of Ensk, on the river bank, a dead postman and a bag with letters were found. Aunt Dasha read one letter aloud to her neighbors every day. Sanya Grigoryev’s lines about distant polar expeditions were especially remembered ...
Sanya lives in Ensk with his parents and sister Sasha. By absurd accident, Sanin's father is accused of murder and arrested. Only little Sanya knows about the real killer, but because of the dumbness, which only later will the miraculous doctor Ivan Ivanovich deliver him, he can do nothing. The father dies in prison, after some time the mother gets married. The stepfather turns out to be a cruel and mean man who torments both children and his wife.
After the mother’s death, Aunt Dasha and Skovorodnikov’s neighbor decide to send Sanya and her sister to a shelter. Then Sanya and his friend Petya Skovorodnikov flee to Moscow, and from there - to Turkestan. “Fight and seek, find and not give up” - this oath supports them along the way. The boys walk to Moscow on foot, but Petkin's uncle, whom they counted on, went to the front. After three months of almost free work with speculators, they have to hide from verification. Petka manages to escape, and Sanya first gets into the distributor for homeless children, and from there - into the school-commune.
Sanya likes school: he reads and sculpts from clay, he makes new friends - Valka Zhukov and Romashka. Once, Sanya helps bring a bag to an unfamiliar old woman who lives in the apartment of the head of the school, Nikolai Antonovich Tatarinov. Here, Sanya meets Katya, a pretty, but somewhat inclined to “ask” a girl with pigtails and dark, lively eyes. After some time, Sanya again finds himself in the Tatarinov’s house: he is sent there for a lactometer, an instrument for checking the composition of milk, Nikolai Antonovich. But the lactometer explodes. Katya is going to take the blame, but the proud Sanya does not allow her to do this.
The Tatarinov’s apartment becomes for Sani “something like the cave of Ali Baba with its treasures, riddles and dangers.” Nina Kapitonovna, whom Sanya helps with might and main, and who feeds him with dinners, is a “treasure”; Marya Vasilievna, “neither a widow nor a husband’s wife”, who always walks in a black dress and often plunges into longing, is a “mystery”; and the "danger" is Nikolai Antonovich, as it turned out, is a cousin of Katya. The favorite topic of Nikolai Antonovich’s stories is a cousin, that is, Marya Vasilievna’s husband, whom he “cared for his whole life” and which “turned out to be ungrateful.” Nikolai Antonovich has long been in love with Marya Vasilievna, but while she is “ruthless” towards him, her geography teacher Korablev sometimes comes to visit. Although, when Korablev proposes to Marya Vasilievna, he is refused. On the same day, Nikolai Antonovich convenes a school council at home, where Korablev is sharply condemned. It was decided to limit the activities of a geography teacher - then he will be offended and leave, Sanya informs Korablev about everything he heard, but as a result, Nikolai Antonovich drives Sanya out of the house. Offended Sanya, suspecting Korablev in betrayal, leaves the commune. After wandering around Moscow all day, he becomes completely ill and ends up in the hospital, where Dr. Ivan Ivanovich rescues him again.
Four years have passed - Sanya is seventeen years old. The school is presenting a staged "trial of Eugene Onegin", it is here that Sanya meets Katya again and reveals her secret to her: he has long been preparing to become a pilot. Sanya finally learns from Katya the story of Captain Tatarinov. In June of the twelfth year, having stopped at Ensk to say goodbye to his family, he went out on the schooner “St. Maria ”from Petersburg to Vladivostok. The expedition did not return.Maria Vasilievna unsuccessfully sent a request for help to the tsar: it was believed that if Tatarinov died, then by his own fault: he “casually handled state property”. The captain's family moved to Nikolai Antonovich. Sanya often meets with Katya: together they go to the rink, to the zoo, where Sanya suddenly encounters his stepfather. At the school ball, Sanya and Katya are left alone, but Romashka interferes with their conversation, who then reports everything to Nikolai Antonovich. Sanya is no longer accepted by the Tatarinovs, and Katya is sent to her aunt in Ensk. Sanya beats Chamomile, it turns out, and in the story with Korablev, he played a fatal role. Nevertheless, Sanya repents of his deed - with a heavy feeling he leaves for Ensk.
In his hometown Sanya finds both Aunt Dasha, and old Skovorodnikov, and his sister Sasha, he learns that Petka also lives in Moscow and is going to become an artist. Once again, Sanya rereads the old letters - and suddenly realizes that they are directly related to the expedition of Captain Tatarinov! With excitement, Sanya learns that none other than Ivan Lvovich Tatarinov discovered the Severnaya Zemlya and named it after his wife Marya Vasilyevna, that it was through the fault of Nikolai Antonovich, this “scary man”, that most of the equipment was unusable. The lines in which the name of Nicholas is directly named are blurred by water and preserved only in Sani's memory, but Katya believes him.
Sanya firmly and decisively exposes Nikolai Antonovich to Marya Vasilievna and even demands that she “bring charges”. Only then Sanya understands that this conversation finally defeated Marya Vasilievna, convinced her of the decision to commit suicide, because Nikolai Antonovich was already her husband by then ... Doctors are unable to save Marya Vasilievna: she is dying. At the funeral, Sanya comes up to Katya, but she turns away from him. Nikolai Antonovich managed to convince everyone that the letter was not about him at all, but about some “von Vyshimirsky” and that Sanya was guilty of the death of Marya Vasilievna. Sanya can only intensely prepare for admission to a flight school in order to someday find the expedition of Captain Tatarinov and prove his case. The last time he saw Katya, he went to study in Leningrad. He studies at a flight school and at the same time works at a factory in Leningrad; both Sasha and her husband Petya Skovorodnikov study at the Academy of Fine Arts. Finally, Sanya seeks an appointment to the North. In the city of the Arctic, he meets with Dr. Ivan Ivanovich, who shows him the navigator’s diaries “St. Mary ”by Ivan Klimov, who died in 1914 in Arkhangelsk. Patiently deciphering the notes, Sanya learns that Captain Tatarinov, sending people in search of land, remained on the ship himself. The navigator describes the hardships of the campaign, with admiration and respect speaks of his captain. Sanya understands that the traces of the expedition must be sought precisely on the Land of Mary.
From Vali Zhukov, Sanya learns about some Moscow news: Chamomile has become "the closest person" in the Tatarinov’s house and seems to be "going to marry Katya." Sanya is constantly thinking about Katya - he decides to go to Moscow. In the meantime, he and the doctor are given the task of flying to the remote camp of Vanokan, but fall into a snowstorm. Thanks to the forced landing, Sanya finds a hook from the schooner “St. Maria". Gradually, from the "fragments" of the history of the captain, a harmonious picture is made.
In Moscow, Sanya plans to make a report on the expedition. But first it turns out that Nikolai Antonovich had already partially outstripped him by publishing an article about the discovery of Captain Tatarinov, and then the same Nikolai Antonovich and his assistant Romashka published in Pravda slander against Sanya and thereby sought to cancel the report. Ivan Pavlovich Korablev helps a lot to Sanaa and Katya. With his assistance, the distrust between young people disappears: Sanya understands that Katya is trying to impose a marriage with Chamomile. Katya leaves the Tatarinov’s house. Now she is a geologist, the head of the expedition.
An insignificant, but now somewhat “settled down” Chamomile is playing a double game: he offers Sanya evidence of the guilt of Nikolai Antonovich if he refuses Katya. Sanya informs Nikolay Antonovich about this, but he is no longer able to withstand the deft “assistant”. With the help of the Hero of the Soviet Union, pilot Ch. Sanya nevertheless receives permission for the expedition, Pravda publishes his article with excerpts from the navigator’s diary. In the meantime, he returns to the North.
They again try to cancel the expedition, but Katya is decisive - and in the spring they should meet with Sanya in Leningrad in order to prepare for the search. Lovers are happy - on white nights they walk around the city, all the time they are preparing for the expedition. Sasha, Sanina’s sister, gave birth to a son, but suddenly her condition worsens sharply - and she dies. For some reason, the expedition is canceled - Sanya is given a completely different purpose.
Five years pass. Sanya and Katya, now Tatarinova-Grigoryeva, live either in the Far East, then in the Crimea, or in Moscow. In the end, they settle in Leningrad with Petya, his son and Katya’s grandmother. Sanya takes part in the war in Spain, and then leaves for the front. Once Katya meets Chamomile again, and he tells her about how he, trying to save the wounded Sanya, tried to get out of the German environment and how Sanya disappeared. Katya does not want to believe Chamomile, in this difficult time she does not lose hope. And indeed, Chamomile is lying: in fact, he did not save, but threw the seriously wounded Sanya, taking away his weapons and documents. Sanya manages to get out: he is being treated at the hospital, and from there goes to Leningrad in search of Katya.
Katie is not in Leningrad, but Sanya is invited to fly to the North, where battles are already taking place. Sanya, having never found Katya either in Moscow, where he simply missed her, or in Yaroslavl, she thinks she is in Novosibirsk. During the successful completion of one of the combat missions, Grigoryev’s crew makes an emergency landing near the place where, according to Sani, one needs to look for traces of Captain Tatarinov’s expedition. Sanya finds the body of the captain, as well as his farewell letters and reports. And having returned to Polyarny, Sanya finds Katya at Dr. Pavlov’s.
In the summer of 1944, Sanya and Katya spend their holidays in Moscow, where they meet with all their friends. Sanya needs to do two things: he gives testimony in the case of convicted Romashov, and in the Geographical Society his report on the expedition, on the discoveries of Captain Tatarinov, about the cause of this expedition died with great success. Nikolai Antonovich is shamefully driven out of the hall. In Ensk, the family gathers again at the table. Old man Skovorodnikov in his speech unites Tatarinov and Sanya: "such captains move forward humanity and science."
