The enemy agents from an unknown nation have secret automated facilities set up in the Atlantic and Pacific oceans for the purposes of sinking ships. The super submarine "Pioneer" and it's intrepid crew is dispatched to find the source of these mysterious sinking's...Unknown to the captain, his chief engineer is working for the bad guys, intent on stopping their efforts, at any cost...It seems the real chief had a twin brother who was a circus acrobat who murdered and replaced him.

Veronika and Boris come together in Moscow shortly before World War II. Walking along the river, they watch cranes fly overhead, and promise to rendezvous before Boris leaves to fight. Boris misses the meeting and is off to the front lines, while Veronika waits patiently, sending letters faithfully. After her house is bombed, Veronika moves in with Boris' family, into the company of a cousin with his own intentions.

1934. After the suppression of the uprising of the Schutzbund workers, engineer Hans Müller leaves Austria and emigrates to the USSR. In Russia Hans finds his love. His relationship with Galina is not simple. Her son Sanka agonizes over the arrival of a stranger in the house. But, in the end, Hans wins the boy's trust. When in Spain begins the Frankist rebellion, Hans voluntarily goes to fight in the ranks of the interbrigade. And after the liberation of Vienna, he returns to his homeland.