Almost any other risk would be preferable.
But he had yet another ground for uneasiness.

He knew well his mother's attachment to young Mr.Heywood, and had taken care she should have no suspicion of the way he was going after leaving her the night he told her the watchword; for such was his belief in her possession of supernatural powers, that he feared the punishment she would certainly inflict for the wrong done to Richard, should it come to her knowledge, even more than the wrath of the marquis.

For both of these weighty reasons therefore he must try what could be done to strengthen Richard in his silence, and was prepared with an offer, or promise at least, of assistance in making his escape.
As soon as the house was once more quiet, he got up, and, thoroughly acquainted with the "crenkles" of it, took his way through dusk and dark, through narrow passage and wide chamber, without encountering the slightest risk of being heard or seen, until at last he stood, breathless with anxiety and terror, at the door of the turret-chamber, and laid his ear against it..