"You come even as I was despairing--nay, when already I had despaired." Sir Crispin was no longer puzzled by the readiness of her acquiescence.
Here was the explanation of it.

Forced by the honesty of her pure soul to abandon the house of a father she knew at last for what he was, the refuge Crispin now offered her was very welcome.

She had determined before he came to quit Castle Marleigh, and timely indeed was his offer of the means of escape from a life that was grown impossible.

A great pity filled his heart.

She was selling herself, he thought; accepting the proposal which, on his son's behalf, he made, and from which at any other season, he feared, she would have shrunk in detestation.
That pity was reflected on his countenance now, and noting its solemnity, and misconstruing it, she laughed outright, despite herself.
He did not ask her why she laughed, he did not notice it; his thoughts were busy already upon another matter.
When next he spoke, it was to describe to her the hollow of the road where on the night of his departure from the castle he had been flung from his horse.