Jack MacHeath, also known as Mac the Knife, is a charismatic butcher and is believed to be the notorious serial murderer, Jack the Ripper. He is also a direct descendant of the 18th-century highwayman MacHeath a.k.a. Mack the Knife.
MacHeath was suspected for being responsible for the White Chapel murders in the 1880s before he escaped England on ship to South America. In April 1910, MacHeath returned to England after a twenty-two year absence and immediately takes to murdering prostitutes again; among them was Lulu. MacHeath's return led intelligence chief Mycroft Holmes to suspect that the murderer may have some connection to one of Thomas Carnacki's vision of a bloodshed waterfront, in which he sent the League to investigate MacHeath.
Eventually, MacHeath was instead caught by the authorities and was about to be hanged without trial as Mycroft was worried that a trial might bring to light the involvement of the 14th Earl of Gurney in the original Ripper murders, whom he was responsible for MacHeath's last victim, Grace, in the 1880s. MacHeath sang his last plea from the gallows until he was vouched by a message from the 14th Earl of Gurney who confesses to all the original Ripper crimes, making MacHeath a freed man. At the same time, Carnacki's vision of bloodshed on the waterfront was not tied to MacHeath but to Pirate Jenny's actions with the Nautilus.
Jack MacHeath is meant to be a decendant of Mack the Knife, from the song with the same name in The Threepenny Opera. The idea of MacHeath's first name Jack, in furthering the connection to Jack the Ripper, is based on Alan Moore's idea. Alan Moore had previously used Jack the Ripper as the focus of his graphic novel From Hell.
"Jack the Ripper" is briefly mentioned in the film adaptation by Rodney Skinner as a comment about the estate on which Dorian Gray lives. In the novelisation, Edward Hyde compliments the Ripper's murders as superior to his own, saying "must have come straight from Hell, and then gone back there", an obvious reference to Alan Moore's other notable graphic novel From Hell.