The titular character, depicted as an insane young man who believes himself to be the overlord of the underworld, demonstrates the ability to predict natural deaths.

Modesty is invited to dinner by René Vaubois, head of the Deuxième Bureau (the French Intelligence Service), on a floating restaurant on the Seine.

Willie, waiting on the river bank for Modesty's return, encounters Chuli, a criminal whose speciality is planting bombs.

Lucifer, a young man with a ruined mind who had been studying to go into the church when he was seduced by a woman and suffered a nervous breakdown, becoming convinced that he was the source of all sin, the devil himself.

A pair of aging puppeteers, Seff and Regina, unable to get work when the music halls closed down, turned to crime.