For the life of him, he could not put from his mind the conviction that Anne Tresslyn was not responsible for her actions.
He was convinced that she had been bullied, cowed, coerced, or whatever you like, into this atrocious marriage, and, of course, there could be no one to blame but her soulless mother.

The girl ought to be saved.

(These are Simmy's thoughts.) She was being sacrificed to the greed of an unnatural mother.

Admitting, for the sake of argument, that she was no longer in love with Braden Thorpe, there still remained the positive conviction that she could not be in love with any one else, and certainly not with that treacherous old man in Washington Square.

That, of course, was utterly impossible, so there was but the one alternative: she was being forced into a marriage that would bring the most money into the hands of the designing and, to him, clearly unnatural parent.
He knew nothing of the ante-nuptial settlement, nor was he aware of the old man's quixotic design in coming between Braden and the girl he loved.
To Simmy it was nothing short of brigandage, a sort of moral outlawry.