Octave de Malivert is graduating from Polytechnique. He is young, bright, elegant, but his strange character worries his mother. She invites him to attend the Mandame salon in Malivert to get him out of his isolation. There he finds his cousin, Armance de Zohiloff. But if the "law of indemnity" which has just been voted to compensate the nobles who consider themselves despoiled by the revolution makes Octave an interesting party, Armance seems to remain insensitive to the young man's attractions. Octave realizes that he is in love with Armance, despite his will and the oath he made to himself never to love. Behind this strange behavior, there is the evil of Octavian, condemned only to platonic love ...