The means he employed were threats.

He had it in his power to make mischief, and in such affairs a woman is so helpless that we may well forgive that which she may do in a moment of panic.

I imagine that he frightened the poor lady into obedience to his command that she should open this door.
Before dinner, when we were all in the drawing-room, I noted a little mark of dust on the white silk skirt of her dress.

At the time I thought only that her maid had been careless.

Perhaps you noticed it, mademoiselle?
Ladies note such things." He turned to Maggie, who nodded her head.
"That," he went on, "was the dust of these old passages.