The teenager Misha Polyakov, being with his mother in a Ukrainian village on vacation with his grandmother and about to return home to Petrograd, offers his best friend Genka to go with him. Suddenly, a white gang of Nikitsky bursts into the village and attacks Misha’s house, where Commissioner Polevoy lives. The purpose of Nikitskiy (aka Nikolskiy) is a dagger located at Polevoy. Saving the commissioner, Misha learns from him the history and secret of the weapon, and receives it for storage with a request to solve the secret. Having returned with adventures to Petrograd, Misha Polyakov with friends begins to unravel the riddle of the dagger, in the handle of which is encrypted text.

"Iskra" is the codename for the plan of the operation of the Soviet troops to break the blockade of Leningrad. In January 1943, the blockade of Leningrad was broken. A corridor 8-11 km wide was formed between Lake Ladoga and the front line.

A story about the tragic events in the life of besieged Leningrad from September 1941 to January 1943.

Sergei Krylov and Oleg Tulin, are promising young physicists in the field of thunderstorms. They dream of weather control. But later their ways in science parted - Oleg is ready to tradeoff his standpoints for personal success, but Sergei knows that the truth is more critical.