water, and each bottle was ornately labelled.
"I've got it!" he almost shouted.
"Got what?"
"The obvious."
And at that moment her uncle, Mark Terrill and the Inspector appeared in the door.
"Mavis—what on earth?" began her uncle in amazement. Then he fumed furiously on the footman. "You scoundrel!" he cried, "what do you think you're doing?"
"Looking for your rubies, Mr. Frosdick," answered the other calmly. Unconsciously she glanced at Mark Terrill, and his eyes had narrowed to pin-pricks. "Moreover, I've found them."
"What!" shouted Mr. Frosdick. "Found 'em. Where?"
"In that bottle of tooth-wash."
For a moment there was dead silence, and then with a snarl of rage Terrill hurled himself at the speaker. But the large young man had a large young fist, and it and Mark Terrill's jaw met to the detriment of the jaw. In fact, the owner of the jaw remained blissfully unconscious on the floor during the next few minutes. And when he did finally stagger to his feet as well as a pair of handcuffs would allow, it was to find the ten wonderful Frosdick rubies ranged on the washstand, while in the basin beside them reposed his ruby red tooth-wash.
"There's your bird, Inspector," said the large young man quietly. "Incidentally this will be enough, but you might ask him about the Duchess of Lampiter's emeralds, and Lady Archer's pearls and a few other trifles."
"Who are you?" snarled Terrill.
"A student of the obvious." answered the large young man with a smile. "And it ought to afford you some amusement during the next few weeks to try and find out in what obvious point you gave yourself away."
Half an hour later, clothed normally once again, the large young man sat down to tea. "I feel I owe you an apology in the first place, Mrs. Frosdick," he remarked, "for substituting my unworthy self for your perfectly good footman. I may say that I'm on the staff of the Tribune, and newspaper men, as you know, are quite unscrupulous. However, to come to the goods! You probably know that during the last two or three years there have been about half a dozen really big jewel robberies. Our friend mentioned the Duchess of Lampiter's emeralds himself last night at dinner. That was one of them.
"Now off and on I've done a good deal of crime reporting, and it interests me. Moreover, I know one or two men at the Yard. And owing to certain points of similarity we became convinced that they were all the work of the same man. I forget who got the idea first, but one day someone took the trouble to get the lists of guests at each of the houses where the robberies had taken place. Some names occurred twice: some even three times, but only one occurred in every list—that of Mr. Mark Terrill. So we began to make inquiries about the gentleman. He apparently knew everybody worth knowing, but who he was and what his parents had been we couldn't find out. He seemed to have emerged into post-War society out of the blue. Before that his history was a blank.
"Well, as we all know, a good-looking bachelor with money can go to most places today. When, in addition, he's a first-class shot and athlete generally he becomes positively in demand. And Terrill was undoubtedly persona grata at most of the big houses. Moreover, there was absolutely nothing against him except the one suspicious fact that he was present at each of the robberies.
"A few days ago I found out that he was coming here for Christmas. And since the Frosdick rubies are well known, I wondered if there was any connection between the two facts. So I thought I'd come too, and try to find out. The difficulty was that, doubtless through an oversight, I hadn't received an invitation. And then there occurred one of those Heaven-sent chances that you read of in books but rarely meet in life. Your new footman is the son of the couple who keep the rooms in Clarges Street where I live.
"Nothing could have suited me better. As footman I knew I'd have to valet Terrill, which was exactly what I wanted to do. So I persuaded him to let me take his place. I had the dickens of a job to do so—he's a first-class fellow: but finally, after taking him round to Scotland Yard to prove I was all right, he consented.
"I got him to give me a few lessons in deportment, applied for leave from the chief, and came here instead of him. And my very first night the rubies disappeared. Well, it was a bit awkward for me. Personally I felt absolutely convinced that Terrill had taken them—the coincidence was altogether too extraordinary. But to feel convinced and have proof are two very different things. And it was quite obvious that suspicion was bound to fall on me. I could have cleared myself, I know—but it might have taken a day or two. And that day or two would have been fatal to any hopes of success. I had to get Terrill with the rubies in his possession. And the point was—where were they? Where had he hidden them?' I knew he had them, but where had he put them?
"Now, in his dressing-case I had discovered a pair of very fine forceps, of the type used by jewellers for gold and silver work. So I guessed that in all probability he had removed the rubies from their setting and disposed of the latter. It was fine work, as I noticed last night, and he could easily have broken it up into small pieces and got rid of it down the bath plug. That left only the separate rubies to hide—a much easier matter for him, and a much harder one for me.
"It was obvious—the hiding-place; it must be. Nothing was locked in his room; I'd examined every drawer. And I was almost in despair. Supposing, now that the search was over, he had them on him. I couldn't accuse him; being the object of suspicion myself it would have looked like a stupid bluff.
"And then suddenly it came to me. There it was right under my nose—the big cut-glass bottle of red tooth-wash. Not that I could see a sign of the rubies; the facets of the crystal and the colour of the liquid prevented that. In fact, it was a marvellous hiding-place, as the obvious generally is. But I knew the rubies were there."
"A very lucky guess," said Mr. Frosdick.
The large young man smiled and lit a cigarette. "No, Mr. Frosdick, not a guess but a certainty."
"But you said you couldn't see 'em."
"Correct," agreed the other. "I couldn't see 'em. But I could see something else which was just as good. Tooth-wash may be for use, and it may be for show. In the first case the level in the bottle diminishes, and in the second it remains stationary. But in neither case does it rise three inches."
"Young fellah," said Mr. Frosdick after a pause, "put it there." He held out his hand. "And since we now have a spare bedroom, the oversight about your invitation is remedied."
That evening Mavis Houghton danced twice with Paul Wetherby and five times with Kenneth Stretton.
"Terrill has one peculiarity which I didn't mention," remarked the latter gravely. "He generally makes love to someone in the house who is closely connected with his hostess. I think it is done professionally to avert suspicion."
"Indeed," she murmured. "How very unromantic."
"Any chance for an amateur?"
Her lips twitched slightly. "The least that a new guest can do is to endeavour to supply the gap left by the departure of his predecessor."
And suddenly he leant towards her. "Mavis—why did you warn me?"
"For a student of the obvious," she murmured, "you seem to be singularly dense."
XII. — THE SECOND RIDE
"THE man who monkeys round with another man's wife is asking for trouble," said the ship's doctor. "And sooner or later he'll get it. He may even have to marry her."
Around us twinkled the lights of Naples: the summit of Vesuvius hung red, glowing in the darkness astern. And peace reigned on board. The ship's bore, with a boat-load of victims, had gone ashore to see the sights; we had the smoking-room to ourselves.
"Mit divorce and all its attendant mud," remarked Murgatroyd, of the Indian Army. "That's the foul part of it."
I