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.