Everyday life of a maritime border guard post in the mid-1930s. On a small Pacific island, a garrison of NKVD border guards is on duty. A small detachment of soldiers bravely defends their homeland from attacks by Japanese saboteurs and drives away uninvited guests. One day, a Japanese destroyer lands troops on one of the Soviet islands. The invaders are aided by traitors they have recruited. But the border guards give the aggressors a worthy rebuff.

A beautiful maiden, Marya Morevna, gives her prospective husband, the mighty warrior Nikita Kozhemyaka, three riddles to solve before she'll marry him. Before he can tell her the answers, the Russian land is invaded by the armies of Kashchei the Immortal, in whose footsteps death and destruction follow. Marya is abducted by Kashchei, and Nikita finds his home in ashes. Nikita meets a kindly wizard who gives him a cap of darkness. With it, the hero will find a way to save his bride and rout Kashchei.

The Second World War. A new L-2 heavy duty gun is being supplied to the Soviet Army. German intelligence needs to seize a new secret weapon.