Colonel Alexandrov for three months at the front. He sends a telegram to his daughter in Moscow, invites them to spend the rest of the summer at the dacha.
The eldest, eighteen-year-old Olga, goes there with things, leaving the thirteen-year-old Zhenya to clean the apartment. Olga is an engineer, she is engaged in music, she sings, she is a strict, serious girl. At the dacha Olga meets a young engineer Georgy Garayev. She is waiting late for Zhenya, but her sister is not there.
And Zhenya at this time, having arrived in the holiday village, looking for mail to send a telegram to his father, accidentally comes to someone’s empty summer cottage, and the dog does not release it back. Zhenya falls asleep. Waking up the next morning, he sees that there is no dog, and next to him is an encouraging note from an unknown Timur. Having discovered a sham revolver, Zhenya plays with him. A blank shot that smashed the mirror frightens her, she runs, forgetting the key to the Moscow apartment in the house and a telegram. Zhenya comes to her sister and already foresees her anger, but suddenly some girl brings her a key and a receipt from the telegram sent with a note from the same Timur.
Zhenya climbs into the old barn, standing in the depths of the garden. There she finds a steering wheel and starts to twist it. And from the wheel go rope wires. Zhenya, without knowing herself, gives signals to someone! The barn is filled with many boys. They want to beat Zhenya, who unceremoniously invaded their headquarters. But the commander stops them. This is the same Timur (he is the nephew of George Garayev). He invites Zhenya to stay and listen to what the guys are doing. It turns out that they help people, especially guarding the families of Red Army soldiers. But they do all this in secret from adults. The boys decide to “do special” Mishka Kvakin and his gang, which climbs in strange gardens and steals apples.
Olga thinks Timur is a bully, and forbids his wife to be with him. Zhenya can not explain anything: this would mean divulging the secret.
Early in the morning, the boys from Timur’s team fill a barrel of a milkwoman with water. Then they put firewood for the other old woman – the grandmother of the brisk girl Nyurki – and find her a missing goat. And Zhenya plays with the little daughter of Lieutenant Pavlov, who was recently killed on the border.
Timurovtsy make an ultimatum to Mishka Kwakin. They order him to appear with his assistant, Figura, and bring a list of members of the gang. Geik and Kolya Bells carry an ultimatum. And when they come for an answer, the Quakans... lock them in the old chapel.
George Garayev rolls Olga –
Have a motorcycle. He, like Olga, is engaged in singing: he plays in the opera of an old partisan. His “severe and terrible” makeup will scare anyone you want, and the joker George often uses this (he owned a sham revolver).
The Timurovs manage to free Geika and Kolya and lock the figure in place of them. They ambush the Kwakin gang, close everyone in the booth in the marketplace and hang a poster on the booth that the “captives” are apple thieves.
In the park – a noisy holiday. George was asked to sing. Olga agreed to accompany him on the accordion. After the performance, Olga encounters Timur and Zhenya walking along the park. An angry older sister accuses Timur of setting Zhenya against her, she is angry with Georgy too: why did not he admit earlier that Timur was his nephew? George, in turn, forbids Timur to communicate with Zhenya.
Olga, in order to teach Zhenya, leaves for Moscow. There she receives a telegram: her father will be in Moscow at night. He only comes for three hours to see his daughters.
And to Zhenya at the dacha comes a friend – the widow of Lieutenant Pavlov. She urgently needs to go to Moscow to meet her mother, and she leaves her little daughter for the night at Zhenya’s. The girl falls asleep, and Zhenya goes to play volleyball. In the meantime, telegrams from my father and Olga come. Zhenya notices telegrams only late at night. But she has no one to leave the girl, and the last train has already left. Then Zhenya sends a signal to Timur and tells him about his misfortune. Timur instructs Kolya Kolokolchikov to guard the sleeping girl – for this I have to tell Kolya grandfather everything. He approves of the boys. Timur himself takes Zhenya on a motorcycle to the city (no one can ask for permission, Uncle in Moscow).
The father is upset that he never managed to see Zhenya. And when the time is nearing three, Zhenya and Timur suddenly appear. Minutes are flying fast – Colonel Aleksandrov needs to go to the front.
George does not find in the dacha no nephew, no motorcycle and decides to send Timur home to his mother, but then comes Timur, and with it Zhenya and Olga. They explain everything.
George comes the agenda. In the form of a captain of tank troops, he comes to Olga to say goodbye. Zhenya transmits the “call sign general”, all the boys from the Timur team are running together. Together they go to see Georgy off. Olga plays the accordion. George leaves. Olga says to the sad Timur: “You always thought about people, and they will repay you the same.”