Medhurst drew a long breath. "Isn't that rather a large order?" he murmured, surprised.
Charles explained to him exactly the sort of services he required. Medhurst promised to comply. "If the man comes near you, I'll spot him," he said, after a moment's pause. "I can promise you that much. I'll pierce any disguise. I should know in a minute whether he's got up or not. I'm death on wigs, false moustaches, artificial complexions. I'll engage to bring the rogue to book if I see him. You may set your mind at rest, that, while I'm about you, Colonel Clay can do nothing without my instantly spotting him."
"He'll do it," Marvillier put in. "He'll do it, if he says it. He's my very best hand. Never knew any man like him for unravelling and unmasking the cleverest disguises."
"Then he'll suit me," Charles answered, "for I never knew any man like Colonel Clay for assuming and maintaining them."
It was arranged accordingly that Medhurst should take up his residence in the house for the present, and should be described to the servants as assistant secretary. He came that very day, with a marvellously small portmanteau. But from the moment he arrived, we noticed that Césarine took a violent dislike to him.
Medhurst was a most efficient detective. Charles and I told him all we knew about the various shapes in which Colonel Clay had "materialised," and he gave us in turn many valuable criticisms and suggestions. Why, when we began to suspect the Honourable David Granton, had we not, as if by accident, tried to knock his red wig off? Why, when the Reverend Richard Peploe Brabazon first discussed the question of the paste diamonds, had we not looked to see if any of Amelia's unique gems were missing? Why, when Professor Schleiermacher made his bow to assembled science at Lancaster Gate, had we not strictly inquired how far he was personally known beforehand to Sir Adolphus Cordery and the other mineralogists? He supplied us also with several good hints about false hair and make-up; such as that Schleiermacher was probably much shorter than he looked, but by imitating a stoop with padding at his back he had produced the illusion of a tall bent man, though in reality no bigger than the little curate or the Graf von Lebenstein. High heels did the rest; while the scientific keenness we noted in his face was doubtless brought about by a trifle of wax at the end of the nose, giving a peculiar tilt that is extremely effective. In short, I must frankly admit, Medhurst made us feel ashamed of ourselves. Sharp as Charles is, we realised at once he was nowhere in observation beside the trained and experienced senses of this professional detective.
The worst of it all was, while Medhurst was with us, by some curious fatality, Colonel Clay stopped away from us. Now and again, to be sure, we ran up against somebody whom Medhurst suspected; but after a short investigation (conducted, I may say, with admirable cleverness), the spy always showed us the doubtful person was really some innocent and well-known character, whose antecedents and surroundings he elucidated most wonderfully. He was a perfect marvel, too, in his faculty of suspicion. He suspected everybody. If an old friend dropped in to talk business with Charles, we found out afterwards that Medhurst had lain concealed all the time behind the curtain, and had taken short-hand notes of the whole conversation, as well as snap-shot photographs of the supposed sharper, by means of a kodak. If a fat old lady came to call upon Amelia, Medhurst was sure to be lurking under the ottoman in the drawing-room, and carefully observing, with all his eyes, whether or not she was really Mme. Picardet, padded. When Lady Tresco brought her four plain daughters to an "At Home" one night, Medhurst, in evening dress, disguised as a waiter, followed them each round the room with obtrusive ices, to satisfy himself just how much of their complexion was real, and how much was patent rouge and Bloom of Ninon. He doubted whether Simpson, Sir Charles's valet, was not Colonel Clay in plain clothes; and he had half an idea that Césarine herself was our saucy White Heather in an alternative avatar. We pointed out to him in vain that Simpson had often been present in the very same room with David Granton, and that Césarine had dressed Mrs. Brabazon's hair at Lucerne: this partially satisfied him, but only partially. He remarked that Simpson might double both parts with somebody else unknown; and that as for Césarine, she might well have a twin sister who took her place when she was Mme. Picardet.
Still, in spite of all his care—or because of all his care—Colonel Clay stopped away for whole weeks together. An explanation occurred to us. Was it possible he knew we were guarded and watched? Was he afraid of measuring swords with this trained detective?
If so, how had he found it out? I had an inkling, myself—but, under all the circumstances, I did not mention it to Charles. It was clear that Césarine intensely disliked this new addition to the Vandrift household. She would not stop in the room where the detective was, or show him common politeness. She spoke of him always as "that odious man, Medhurst." Could she have guessed, what none of the other servants knew, that the man was a spy in search of the Colonel? I was inclined to believe it. And then it dawned upon me that Césarine had known all about the diamonds and their story; that it was Césarine who took us to see Schloss Lebenstein; that it was Césarine who posted the letter to Lord Craig-Ellachie! If Césarine was in league with Colonel Clay, as I was half inclined to surmise, what more natural than her obvious dislike to the detective who was there to catch her principal? What more simple for her than to warn her fellow-conspirator of the danger that awaited him if he approached this man Medhurst?
However, I was too much frightened by the episode of the cheque to say anything of my nascent suspicions to Charles. I waited rather to see how events would shape themselves.