Ukraine. 1920. The Civil is in full swing. The Bolsheviks are confronted with the most active resistance in Kholodniy Yar. The home parts of Hetman Bohdan Khmelnytsky and Haydamaky ottomans are proclaimed as the so-called Kholodnoyarska Republic. The 15,000-strong united troops led by local ottomans control the major part of Cherkassy oblast. They look forward to news from the 100,000-strong Ukrainian-Polish Army concentrated at the western border. The Bolshevik propaganda labels Symon Petlyura and the Kholodniy Yar ottomans as looters and pogrom brigands. The local department of Cheka headed by Comrade Marconi has a multi-move scheme aimed at discrediting the Ukrainian anti-Bolshevik movement in the eyes of Europe and the rest of the world. The Kremlin invites a group of foreign journalists who are supposed to expose the Kholodniy Yar "brigands". One of them is a Romanian newspaper correspondent named Radulescu. But his real name is Dibrova and he is Petlyura's Cossack captain and resident and his mission is to coordinate the Kholodniy Yar ottomans' activities. He secretly gets off the train at the Kamyanka station. He overhears a conversation between Cheka officers from which he finds out that there is a mole in the Kholodniy Yar commanding staff and that his name (or nickname) is Kochubey. The agent's picture is shown on a Bolshevik poster among 13 rebel leaders, but Dibrova cannot see which face is Kochubey's. Dibrova understands that under the circumstances he cannot appear at the rebel headquarters: there is a mole, so any plans will be known to the enemy. He cannot sneak into the rebel camp disguised as a private, either: Marconi knows him by his distinctive mark: he is one-armed. Dibrova manages to contact Ataman Ruchka: he knows the man very well, and he did not see Ruchka's face on the poster which means he is not the mole. Ruchka's daughter Maria enlists as a nurse in a Bolshevik field hospital. She manages to get to the basement where Cheka keeps captive rebel ottomans suffering from typhus. A conversation with Petro Haydamaka narrows the circle of suspects to four. Besides the Dibrava-Marconi standoff, the film features a fierce battle between the Bolshevik and Ukrainian nationalist propaganda machines brought up by printed rhymed pamphlets. The plot leads to a discovery that the mole is the main author of the pamphlets and that the exchange of leaflets is, in fact, a means of communication between Marconi and Kochubey. This channel of communication is codenamed "Marconi Option". With the help of the mole the Cheka manages to provoke a big pogrom. Foreign journalists see its consequences. As a result, Europe denies Petlyura any military or financial aid. Nevertheless, even knowing that they are doomed, the Kholodniy Yar rebels stand up to confront the Bolshevik enemy. They are defeated but unbroken.