After the arrest of a member of “The People’s Will” party Sergei Degaev in December 1882, the Inspector of the Secret Police Georgy Sudeikin managed to make him his agent provocateur. The information then received from this agent allowed the police to neutralize many of his former comrades in the revolutionary underground. Vera Figner was among the first arrested. The question of the total number of persons whom Degaev betrayed to the police was not specifically addressed in historiography, mainly because the notebook where Degaev recorded who and when he exposed to the police was not preserved, and therefore there is no direct evidence to prove the specific involvement of Degaev in the arrest of each particular member of “The People’s Will” who was identified and neutralized by the police in 1883. The article is based on the previously unpublished materials of the Police Department from the State Archive of the Russian Federation as well as personal sources, and reconstructs, as accurately as possible, the picture of Degaev’s provocative activities. Furthermore, the article specifies the number of members of “The People’s Will” betrayed by Degaev and also restores the names of some of them. In addition, the article identifies certain structures of conspirators and names their contacts destroyed after their disclosures by Degaev. In particular, the Kharkov printing house was disclosed, and its employees were arrested. The police also destroyed the mechanism of contacts between the prisoners of the Peter and Paul Fortress and on the outside. Based on the results of the study, conclusion was made of an estimated number of persons who were betrayed to the police by the provocateur Degaev: there were at least 80 of them. By further studying the records of the Police Department, retrieving from them the information which implicitly proves Degaev’s involvement in the disclosure of “The People’s Will” clandestine network, and comparing these data with details from personal sources it seems feasible to verify some more persons betrayed to the police by this provocateur.