For several years as a terrible sea monster drowns ships of the Navy. In a small number of ships that managed to survive, in the sides were found huge holes triangular shape. Now any exit to the sea is deadly, so America sends a special frigate called Blue Star. His goal is to find and destroy the terrible monster. One of the participants of the punitive expedition is a famous Professor from France – Pierre Aronnax. He has a deep knowledge of the mysteries of the deep sea. The search for the monster continues for more than three months, but in the end, the frigate still detects it and immediately starts the attack mode. After an unsuccessful battle with the monster ship goes to the bottom, and the Professor, his servant Conseil and whaler Ned Land get on a submarine and make an amazing journey under water.

Soviet spies are delivering top-secret mail to Moscow.