Mid 1930s On a small Pacific island at the entrance to Zolotaya Bay, there is a garrison of the NKVD border guard. The son of the lighthouse keeper Fyodor Burov arrives on the island with a spy mission. One morning, he sets fire to the lighthouse and takes a boat to the sea. The Chekist border boat team is given the task of meeting uninvited guests disguised as a fishing boat. A schooner with Japanese saboteurs is captured, and the Chekist leads her away. On board the schooner, Fyodor Burov gets discovered and detained. Meanwhile, a Japanese warship is landing on the island. A small detachment, commanded by senior lieutenant Nazarov, manages to restrain the onslaught of the enemy before the appearance of border guards and bomber planes.