And he isn't always that way, either.

There are times when he's so strange--so different! I don't believe he understands himself then.

There seems to be a wild fire in him, that once in a while blazes up, and scorches and frightens him as well as other people." Sophie was perhaps more interested in this extravaganza of Cornelia's than if she had known the incident upon which it was mainly founded; but, on the other hand, it is possible that less exaggerated language would not have given her so correct an idea of Bressant's character.
Cornelia--there being nothing else to especially occupy her thoughts--had allowed them to run a good deal upon Bressant, and upon what happened by the fountain in the garden: perhaps she had mingled the real things and events with the fantasies of her dreams, and thus built up an impression and theory in regard to the young man considerably more picturesque than was warranted by the premises at her command.

All this would have been done involuntarily; and possibly Sophie's question elicited the first conscious perception and statement of what Cornelia's opinion had grown to be.

But unconscious judgments are often more accurate than deliberate ones because there is more of intuition about them.
Be that as it may, from the moment Sophie imbibed the idea that there was something strange, fierce, and ungovernable in Bressant's nature, she felt her sympathy and interest moved and aroused.