The TV series "The Enigma of Euclid" is a continuation of the detective story about the brilliant mathematician Olga Barkovskaya, who helps investigator Kartashova solve the most intricate and mysterious cases. One such case conveniently presents itself: someone kidnaps lawyer Gennady Sinitsyn and murders his wife Natalia. The criminal leaves clues for the detectives - tables with mysterious sequences of perfect numbers. Olga manages to decipher one of them...