Russia in the early 18th century: Naval officer Plakhov has fallen in love with a young woman. When she is threatened by a stranger, he kills him and is thereby sentenced to death. However, the head of the secret service decides to send Plakhov on a mission instead.

These are the dark times around 1720 in Russia. Tsar Peter the Great dies and his highly esteemed partner and friend Prince Menshikov rules the country from now on. But there are also those who oppose the prince. Messenger Ivan, an army officer, fails one of the risky resistance orders given to him by the scheming opposition and openly confesses to it. He is to be punished mercilessly, but the head of the secret service recognizes the officer's qualities, and from now on Ivan becomes an agent of the Tsar. Thus begins a series of mysterious incidents and he begins to investigate them. Masons, pirates and grand dukes, all have their dark secrets...