"In adapting the most important thing - to find the salt, the essence of the story that touches the audience, how to convey emotion on screen.

The series stars Viktoriya Isakova as Anna Zimina, a Federal Security Service (FSB) officer, and Vladimir Mashkov as Alexey Bragin, a Russian Marine Corps sniper.

Anna comes to believe that Alexey, who was held captive by Chechen terrorists as a prisoner of war, was "turned" by the enemy and threatens the Russian Federation.

Marine Colonel Alexey Bragin and sniper Yuri Khamzin go missing during a military operation in the North Caucasus.

Six years later, a joint force of the FSB's Alpha Group and Spetsnaz GRU raids a terrorist camp in the North Caucasus.

Physically and psychologically exhausted by long years of torture and solitary confinement, Bragin begins working with doctors and psychologists, as well as Anna Zimina, an expert analyst from the FSB's Counterterrorism Center.

At the heart of the plot is a confrontation between Bragin, who is experiencing post-traumatic stress disorder and is suspected of recruiting terrorists, and Anna, the FSB officer assigned to investigate him.

While the rest of the FSB and the political establishment believe Bragin to be a war hero, Anna is worried that he has been recruited and brainwashed by Chechen chief Bin Jalid to act as a sleeper agent.

She begins an illegal audio and video surveillance of Bragin's home hoping to catch him at something to prove her suspicions correct.

Unbeknownst to his family or Anna, Bragin converted to Islam during his captivity, and prays daily in his storage in private.

After being tipped off by an anonymous contact, they are go on the run where the husband is killed and the wife tries to escape to Estonia, where she is captured by Mikhail.

Flashbacks show that Bragin had been taken out of captivity by Jalid in order to teach his son, Mussa, to speak Russian.

At the event (taking part in the Red Square), Yuri Khamzin assassinates one of Basov's aides, forcing all the dignitaries, including Bragin, to flee into Lenin's Mausoleum.

The series was produced by Timur Weinstien's WeiT Media Production company and the first episode was premiered on Monday, March 16, 2015, on Russia-1 Federal Channel.