Three naval cadets accidentally get possession of a secret diary that was stolen from Bestuzhev, a vice-chancellor of Russia. If this diary ever gets abroad, the consequences for the country would be grave. The cadets are trying to return the papers to their owner, but there are others who want to get the papers...

In the second movie the Naval Cadets are guarding the princess coming from Germany to marry a Russian prince.

In the third movie the Naval Cadets are still servicing the homeland - this time during a Seven Years War.