In this book, Hugo introduces us to a number of Paris criminals — in particular, to Babet, Claquesous, Gueulemer, and Montparnasse, who governed the Paris underworld from 1830 to 1835. Gueulemer is a stupid strong man, thief, and murderer. Babet is a former tooth-puller who has also sold plaster busts and shown freaks at fairs; he is thin, supple, and absolutely without morals. Claquesous is a ventriloquist behind a mask; Montparnasse is young, good-looking, and ruthless. Thanks to their various skills and their close relations, they have practically a monopoly of crime in the department of the Seine. With them work a number of other minor criminals, of whom Boulatruelle, the ex-convict we already met at Montfermeil, is one.
In an epic description that perhaps may owe something to Dante's Inferno, Hugo now introduces us to the world that lies even below that of Les Misérables — the lowest depths of the criminal poor. The study of criminal life fascinated many nineteenth-century authors. Balzac has several novels in which the master criminal Vautrin appears; Dickens has his Fagin; and a number of popular French authors like Eugene Sué made adventures in the underworld their stock in trade.
Like most nineteenth-century reformers, Hugo is an environmentalist — that is, he believes that man is, on balance, naturally inclined to good, and that the evil in him is a product of his treatment by society. Crime, he says at the end of Chapter 2, will vanish with enlightenment. However, Hugo the writer is wiser than Hugo the theoretician, and in Book VIII he will invalidate everything he has said in Book VII by showing us a man whose criminality is not the result of his environment, and who is villainous as naturally as he breathes.