The search for "enemies of the people" and "agents of foreign intelligence" seems to be a generic sign of the Stalinist regime. However, the hysteria of spy mania was fueled in our country during the First World War. What was the revolutionary movement in the Navy and how did they fight it? Where is the line between true and imaginary espionage? Is thought crime, sympathy for the enemy treason? And where is the thin line separating the defense of the Fatherland and judicial repression? The book "Ghosts of Treason" is devoted to the work of Russian special services in the Baltic Fleet and in the Baltic States in 1910-1917. The publication includes unique memoirs and testimonies of the head of the gendarmerie in the Baltic, Lieutenant Colonel V.V. Vladimirov, and documentary materials of his investigations. For the first time, a list of secret officers of the tsarist special services who worked in the Baltic Fleet is published.