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.