Arina dreams of dedicating her life to the Motherland. Zoya wants to escape from the cruel felon Voron. Zoe accidentally becomes an accomplice to the gruesome robbery of Arina's family. Both girls end up in prison.
The girls arrange a transfer from prison into the intelligence agency. Arina gladly accepts the offer. Zoya does as well, but only to avoid punishment. The girls begin to study with the other secret agents in training. Arina excels in all subjects, except for physical training, while Zoe has no problems. Arina despises Zoya during training and attempts to frame her. Zoya manages to elude.
The War begins. The girls are sent on their first mission. In occupied Riga they must find a Soviet scientist, Professor Serebrov, and ensure safe extraction back to Moscow. Arina and Zoya are not happy with their joint assignment, but they don't contest the orders and follow through.
The girls are forced to put aside their animosity in order to fulfill the mission, despite the danger. Zoya hopes Arina will forgive her and become rebuild their relationship as friends. But Arina makes it clear: Zoya will always be her enemy.
Arina and Zoe stay in Kiev under the disguise of nuns. Their mission is to find a downed Soviet plane near the city. A military engineer was carrying classified documents about the trials of Katyusha on it. The spies must find the plane and destroy the documents, before they fall into the hands of the Germans.
Arina faces a difficult choice. Zoya, whom she hates with all her heart, has been captured by the Germans and needs to be rescued. Arina manages to look past her feelings and attempts to convince a young lieutenant to attack the Germans and save Zoya.
The year is 1943. Arina, Zoya and Petrov are sent on their next mission. In Polotsk, a German reserve division is is about to become active. It is extremely important to find out where the division will be sent. Voron is now based in Polotsk and is aware that Zoya is a spy. Voron is preparing to benefit from this information.
The girls have to flirt with the German staff officers in order to extract information, but deeper relationships develop. For the fulfillment of the task, Arina has to marry Rickert, and circumstances become complicated. Voron threatens the spies and demands money.
The year is 1944. Arina is no longer the political idealist she was during the start of the war. While Zoya grows to appreciate everything that the Soviet government has done for her. Arina asks for a new assignment. She wants to fight and no longer work in intelligence. The Soviet troops begin their approach to Poland.
Arina falls into the hands of the Poles. Because of an assassination attempt, her identity is revealed. However, Arina cleverly manipulates Zbignev manages to disrupt the unification of the Polish against the Soviets. Arina is no longer in danger.
Saving herself and Volodya, Arina escapes from Poland. Her actions speak on the fate of Petrov and Zoya who are both in prison. Arina gets her hands on a secret list of double agents and uses this knowledge to her advantage.
Arina offers a deal to the Soviet commanders. Moscow accepts the offer, but decides to arrest the spy. To complete the mission they send Zoya and Petrov who are against the orders to terminate Arina and act on their own.
