Then: "There's something I've been trying to figure out," he recommenced, speaking more to himself than to Claire.

"There must be some sort of sense to all the signaling Hade does when he comes out of this swamp, onto your lawn.

If it was only that he doesn't want casual visitors to know he has come that way, he could just as well go around by the road to the south of the swamp, and come openly to the house, by the front.
And, if things are to be moved to or from the house, they could go by road, at night, as well as through here.

There must be something more to it all.

And, I have an idea I know what it is ....