It is probable that the young girl had rejected his advances.

Lank and pale, with ill-proportioned limbs and face all awry, he revenged himself upon her for his own ugliness, and the contempt which the handsome, vigorous girl must have evinced for him.

He ardently longed to induce his father to send her about her business; and for this reason he was always spying upon her.
For some time past, he had become aware of the meetings with Silvere, and had only awaited a decisive opportunity to reveal everything to his father, Rebufat.
On the evening in question, having seen her leave home at about eight o'clock, Justin's hatred had overpowered him, and he had been unable to keep silent any longer.

Rebufat, on hearing his story, fell into a terrible rage, and declared that he would kick the gadabout out of his house should she have the audacity to return.

Justin then went to bed, relishing beforehand the fine scene which would take place on the morrow.