During the demolition of the Moscow Intourist Hotel, workers find an audio cassette under the floor with a recording of a strange conversation and take it to the FSB. Analysis shows that this is a recording of a recruiting conversation that took place 30 years ago. Young lieutenant Evseev is searching for a recruited spy, which is intertwined with the adventures of diggers in the mysterious Moscow dungeons, the work of the CIA, looking for approaches to Russian state secrets, the everyday life of Lilliputian prostitutes... In the end, Evseev finds a spy device installed at one of the training grounds in the seventies, arrests a high-ranking military man... But is this the same person who was recruited three decades ago?