"Very probably." Cleek's detached air seemed to dismiss the affair. His eyes were fixed upon one of the Bunsen burners beneath which stood a retort labelled plainly enough, "Nitrous Oxide." Casually he picked up a strand of hair and seemed to cast it away, absent-mindedly. Suddenly he switched round upon his heel. "Did you have that headache last night?" he asked, his hand resting for a moment upon the retort. "No, I didn't notice it, but I was so dead beat that I simply flung myself down and slept like a log." "H'm," Cleek said, thoughtfully. "Well, Captain, there is very little to be gained here. Still, I should like to go through some of the rooms of the house myself, if you've no objection." "Why, of course not. Do as you please. But it's no use suspecting the servants because they couldn't get past the guard, and----" "I suppose not. But I'll have a talk with that guard, too, if you don't mind. It's as well to take all precautions." "By all means." Cleek followed the Captain out of the room and into the drawing-room, now empty save for the guard in question, a big man in soldier's uniform who saluted as they came up to him. The Captain spoke first: "Marshall, this gentleman would like to know if any one came in here last night," he said, quietly. "Speak out." "No, sir." The man's voice was rough and emphatic. "Only yourself--and that but for a moment." "_Myself?_" Captain Digby's voice registered utter amazement. "You're dreaming, man. I was never down here last night, I'll swear----" "Beggin' yer pardon, but yer were, sir," responded Marshall, stoutly. "You just switched on your torch, saying you'd forgotten something, and was in and out before you could say Jack Robinson. You've 'ad so much on your 'ands, sir, it's no wonder you forget. Nothin' wrong, is there?" Cleek's quick voice interposed before the Captain had time to reply, but his dazed, blank face answered for him. "No, Marshall, there's nothing wrong at all. Everything, in fact, is quite in order. The Captain forgot, I expect. That's all I wanted to ask you. Better come along upstairs, Digby. I'd like to have a word with your father when I come down, but if you'll be good enough to show me the way upstairs now----" The dazed look was still upon the Captain's face as he led Cleek upstairs, and at sight of it that gentleman gave vent to a low, amused laugh. "Don't worry, Captain," he said, softly. "Keep quiet and don't get disturbed about it. Every cloud has a silver lining, you know, and I've an idea that this one has a touch of gold in it." He said no more, and the two went from room to room, through bedroom and bathroom, nursery and servants' quarters, until at last Cleek expressed himself satisfied, and consented to join Colonel Digby in the library. They found him engaged in looking over the letters which were to go by that night's post.