The series is based on real events and is dedicated to the story of the poisoning of a former employee of the Russian Federal Security Service (FSB) and the KGB. In the autumn of 2006, Alexander Litvinenko suddenly began to feel unwell and was urgently hospitalized. Three weeks later, he passed away. It was discovered that he had been poisoned with a rare and almost undetectable radioactive substance. Litvinenko's death became the reason for one of the most complex and dangerous investigations in the entire history of the capital's law enforcement officers' service.