"Mr. Nisbet requires his assistance again," I suggested.
"That is the natural inference, and we have to discover the exact nature of this required assistance. If bold measures are necessary we must adopt them."
"I am ready. Have you any theory as to Molly?"
"I can think of more than one. The girl was young at the time of the lady's death; Barbara is by no means bad looking; Molly was pretty, I dare say; she was poor, she was ignorant; Mr. Nisbet may have taken a fancy to her----"
I interrupted him. "No, Mr. Rivers, I cannot entertain the theory that Molly consented to become Mr. Nisbet's mistress."
"I will not force it upon you," said he dryly, "but perhaps I am a better judge of human nature than yourself. However, we shall soon discover something; we shall not be kept long in the dark."
We had little difficulty in finding the house inhabited by Mr. Nisbet, and its appearance deepened my apprehensions. In saying that we found the house I am not quite exact, for a high wall surrounded it, and only the gables could be seen. This wall was of surprising extent, and could have occupied not less than an acre of ground. It was of stone, and might have been built round a prison. We walked cautiously around it, keeping close in its shadow and prepared at any moment to stroll carelessly away in the event of an inmate issuing from either of the gates--one in the front, the other in the rear--which afforded ingress to it.
Night had fallen, and there was no moon, so that we were comparatively safe from observation, but this did not make us less cautious in our movements. We were waging our silent battle with a wary foe, and to be taken unaware would be fatal to us.
There was no other house near the building. At no great distance were towering ranges of rock and tree which intensified the gloom of the habitation. Retreating to a hillock we ascended it, and from that height perceived lights in some of the upper windows.
"A pleasant residence," said Mr. Rivers, with a slight shiver. "One can imagine any deed of darkness being perpetrated within those walls. Hush! Don't move!"