He had not long to remain in doubt. The man lifted his head presently, and looked up towards the lighted window; then, with the agility of some wild animal, sprang from the barge to the garden-wall. There Lucius lost him in the darkness. Presently there came a long whistle—long but not loud; then a light appeared in the lower part of the house—a light from an open door, evidently. Lucius saw the light appear and vanish, and heard the closing of a heavy door. Some one had admitted that man to the house, but who was that some one? There was foul play of some kind; but what the nature of the mystery was a question he could not answer. What should he do? Go round to the front gate, ring, and alarm the household? By that means only could he solve the mystery, and prove to Lucille that these Winchers, whose fidelity she believed in, were deceiving her. Yet to do that might be to imperil his patient, in whose weak state any violent shock might be well-nigh fatal. Reflection convinced him that whatever mischief was at work in that house was of a subtle character. It could only mean plunder; for after all, to suppose that it involved any evil design against Homer Sivewright’s life seemed too improbable a notion to be entertained for a moment. The plot, whatever its nature, must mean plunder, and these Winchers, the trusted servants, in whom long service seemed a pledge of honesty, must be the moving spirits of the treason. What more likely than that Jacob Wincher, who knew the value of his master’s treasures, was gradually plundering the collection of its richest gems, and that this stealthy intruder, who entered the house thus secretly under cover of night, was his accomplice, employed to carry away and dispose of the booty? Arguing thus, Lucius decided that it would be a foolish thing to disturb the evildoers in the midst of their work. His wiser course would be to lie in wait, watch the house till daybreak, and surprise the accomplice in the act of carrying off the plunder. As the man had gone in, so he must surely come out before morning. If, owing to the darkness of the night, he should escape the watcher’s keen gaze on this occasion, Lucius determined that he would set one of the minions of Mr. Otranto, the private detective, to watch to-morrow night.