In 1761, Catherine travels to Russia and becomes the Empress by marrying the Emperor of Russia, Peter. With hopes of marrying a great love, Catherine soon realizes Peter is a selfish brat who stands against everything she values. Catherine is feeling hopeless and verging on suicide when her servant, Marial, presents her with an alternative path – to overthrow Peter.
Catherine takes her first steps toward a coup. Taking advice from Marial, she attempts to seduce and recruit palace intellectual Count Orlo. It’s a disaster. However, after seeing Peter’s brutal treatment of local nobles and unwillingness to listen, he decides to join Catherine’s coup.
Catherine, Orlo and Marial continue their coup planning. They try to recruit an unhappy military general, Velementov, for their cause during palace celebrations honoring Peter’s late father, Peter the Great. Peter, noting Catherine’s unhappiness at court, gifts Catherine a sterile lover, Leo. She’s hesitant at first, but Leo manages to charm her.
Catherine tries to manage her reputation at court and her relationship with Leo, both of which distract her from the coup. Meanwhile, the influential Patriarch of the church dies, and a new one must be chosen. Orlo sees an opportunity to try and influence Peter in the decision, and Archie makes moves.
As the war with Sweden continues to rage, Catherine and Aunt Elizabeth visit the military at the Russian front. Seeing the soldiers reminds Catherine of her goal to rule Russia differently. Grigor struggles with Peter and Georgina’s relationship and poisons Peter to end it. When Peter falls ill, Velementov, Orlo, and Marial all try to influence Catherine’s steps toward takeover as Peter’s life hangs in the balance.
Peter has a new lease on life after his near-death experience. He is open to Catherine’s progressive ideas of introducing art and science to court and wants to focus on an heir. Orlo tries to figure out who poisoned Peter and faces demons of his own.
Catherine feels optimistic about peaceful coexistence with Peter and their increasing chemistry. When smallpox breaks out in the servant’s quarters, however, Peter reverts to his old ways. Meanwhile, Leo and Catherine’s relationship suffers and Georgina misses Peter.
Catherine’s political abilities are tested when she’s given an opportunity to travel abroad with Peter and Velementov to discuss ending the war with Swedish king. Velementov finally sees the potential of her leadership and decides to support the coup. Back at the palace, Leo wants to leave court. Marial tries to keep him there by telling him about the coup.
Tensions mount as Catherine, Orlo, Velementov, Leo, and Marial try to get regional counts on board with the coup. A few of the men end up killed. When a body is discovered later, Peter decides to torture everyone at the palace to find the murderous traitors. Marial buckles under the pressure and confides in Archie about Catherine’s plans. Catherine realizes she is pregnant.
Catherine’s decides to move forward with the coup on her birthday. Peter isn’t so easily overcome and holds Leo hostage as collateral. In exchange for a return to her status, Marial betrays Catherine to Peter and tells him that she is pregnant. Catherine realizes that the only chance for a greater Russia is to fight, without Leo. The battle begins.