As the Soviet Union's resident Hannibal Lecter, Andrei has killed a lot of people.
Though the novel depicts several of Andrei's murders, it's his forty-fourth victim—Child 44—who sparks Leo Demidov's investigation. Leo had actually been assigned with covering up the murder, as the government refuses to acknowledge that such crimes can exist in Soviet society, which is supposed to make life perfect for everyone. As Leo begins to notice a pattern in these killings, however, he sets out to bring down the murderer once and for all.