His son had openly defied his authority and was going to marry the daughter of his enemy.

He must do something to prevent it; the marriage must not take place, but what could he do?
The boy was of age and legally his own master.

He could do nothing to restrain his actions unless they put him in an insane asylum.

He would rather see his son there, he mused, than married to the Rossmore woman.
Presently there was a timid knock at the library door.

Ryder rose from his seat and went to see who was there.