I felt, however, that Seabury accepted this conclusion reluctantly, in fact with a sort of mental reservation not to cease activity himself.

The remainder of the forenoon, and for some time during the early afternoon, Craig plunged into one of his periods of intense work and abstraction at the laboratory.

It was, indeed, a most unusual and delicate test which he was making. For one thing, I noticed that he had, in a sterilizer, some peculiar granular tissue that had been sent to him from a hospital. This tissue he was very careful to cleanse of blood and then by repeated boilings prepare for whatever use he had in mind.

As for myself, I could only stand aside and watch his preparations in silence. Among the many peculiar pieces of apparatus which he had, I recall one that consisted of a glass cylinder with a siphon tube running into it halfway up the outside. Inside was another, smaller cylinder. All about him as he proceeded were glass containers, capillary pipettes, test tubes, Bunsen burners, and dialyzers of porous parchment paper whose wrappers described them as "permeable for peptones, but not for albumins."

Carefully set aside was the blood which he had drawn from Seabury's veins, allowed to stand till the serum separated out from the clot. Next he pipetted it into a centrifuge tube and centrifuged it at high speed, some sixteen thousand revolutions, until the serum was perfectly clear, with no trace of a reddish tint, nor even cloudy. After that he drew off the serum into a little tube, covered it with a layer of a substance called toluol from another sterile pipette, and finally placed it in an incubator at a temperature of about ninety-eight.

It was well along toward four o'clock when he paused as if some mental alarm clock had awakened him to another part of the plan of action he had laid out.

"Walter," he remarked, hastily doffing his stained old laboratory coat, "I think we'd better drop around to the Vanderveer."

Curious as I had been at the preparations he was making in the laboratory, I was still glad at even the suggestion of something that my less learned mind could understand and it was not many seconds before we were on our way.

Through the lobby of the famous new hostelry we slowly lounged along, then down a passage into the tea room, where, in the center of a circle of quaint little wicker chairs and tables, was a glossy dancing floor.

Kennedy selected a table not in the circle, but around an "L," inconspicuously located so that we could watch the dancing without ourselves being watched.

At one end of the room an excellent orchestra was playing. I gazed about, fascinated. At the dancing tea was represented, apparently, much wealth—women whose throats and fingers glittered with gold and gems, men whose very air exuded prosperity—or at least its veneer.

About it all was the glamor of the risquÉ. One felt a sort of compromising familiarity in this breaking down of old social restraints through the insidious influence of the tea room, with its accompaniments of music and dancing.

"I suppose," remarked Craig after we had for some time settled ourselves and watched the brilliant scene, "that, like many others, Walter, you have often wondered whether these modern dances are actually as stimulating as they seem."

I shrugged my shoulders non-committally.

"Well, there is what psychologists might call a real dance neurosis," he went on, contemplatively, toying with a glass. "In fact few persons can withstand the physical effect of the peculiar rhythm, the close contact, and the sinuous movements—at least where, so to speak, the surroundings are suggestive and the dance becomes less restrained and more sensuous, as it does often in circumstances like these, often among strangers."

The music had started again and one after another couples seemed to float past in unhesitating hesitation—dowager and dÉbutante, dandy and doddering octogenarian.

"Why," he exclaimed, looking out at the whirling kaleidoscope, "here in the most advanced epoch, people of culture and intelligence frankly say they are 'wild' for something primitive."

"Still," I objected, "dancing even in the wild, stimulating emotional manner you see here need not be merely an incitement to love, need it? May it not be a normal gratification of the love instinct—eroticism translated into rhythm? Perhaps it may represent sex, but not necessarily badly."

Kennedy nodded. "Undoubtedly the effect of the dances is in direct ratio to the sexual temperament of the dancer," he admitted.

He paused and again watched the whirl.

"Does Mrs. Seabury herself understand it?" he mused, only half speaking to me. "I'm sure that this Sherburne is clever enough to do so, at any rate."

A hearty round of applause came from the dancers as the music ceased. None left the floor, however, but remained waiting for the encore eagerly, scarcely changing the positions in which they had stopped.

"To my mind," Kennedy resumed, with the music, "several things seem significant. Many people have noticed that after marriage women generally lose much of their ardor for dancing. I feel that it is an unsafe matter on which to generalize, but—well—Mrs. Seabury seems not to have lost it."

"Then," I inquired quickly, "you imply that—she is not really as much in love with her husband as she would have us think—or, perhaps, herself believes?"

"Not quite that," he replied doubtfully. "But I am wondering whether there is such a factor that must be considered."

Before I could answer Kennedy touched my arm. Instinctively I followed the direction of his eye and saw Mrs. Seabury step out on the floor across from us. Without a word from Craig, I realized that the man with her must be Sherburne, our "tango thief."

Fashionably dressed, affable, seemingly superficially, at least, well educated, tall, graceful, with easy manners, I could not help seeing at a glance that he was one of the most erotic dancers on the little floor.

As they passed near us, Mrs. Seabury caught Kennedy's eye in momentary recognition. Her face, flushed with the dance, colored perhaps a shade deeper, but not noticeably to her partner, who was devoting himself wholly and skillfully to leading her in a manner that one could see called forth frequent comment from others, less favored.

As they sat down after this dance and the encore, Craig motioned to the waiter at our table and whispered to him.

A few moments later, a man whom I had seen around the hotel on my infrequent visits, but did not know, slipped quietly into a seat beside Kennedy, even deeper in the shadow of the recess in which we were sitting.

"Walter, I'd like to have you meet Mr. Dunn, the house detective," whispered Kennedy under his breath.

The usual interchange of remarks followed, during which Dunn was evidently waiting for Kennedy to reveal the real purpose of our visit.

"By the way, Dunn," remarked Craig at length, "who is that fellow—over there with the woman in blue—the fellow with the heavy braided coat?"

Dunn craned his neck cautiously, then shrugged his shoulders. "I've seen him here with her before," he remarked. "I don't know him, though. Why?"

Briefly Kennedy sketched such facts of a supposedly hypothetical case as would be likely to secure an opinion from the house man. Dunn narrowed his eyes thoughtfully.

"That's rather a ticklish situation, Kennedy," Dunn remarked when Craig had stated the case, omitting all reference to Seabury's name as well as his suspicions. "Of course," he went on, "I know we've got to protect the name of the hotel. And I know we can't have men meeting our women patrons, doing a gavotte or two—and then fox-trotting them into blackmail."

Dunn stroked his chin thoughtfully. "You see, we can do a great deal to suppress card sharps, agents for fake mining stocks, passers of worthless checks, and confidence men of that sort. But it is not so simple to thwart the vultures who prey on the gullibility and passions of the so-called idle rich."

"There must be something you can do to get it on this fellow, though," persisted Craig.

"Well," considered the house man, "we have what might be called our hotel secret service—several men and women operating entirely apart from the hotel force of detectives who, like myself, are too well known to clever crooks. Nobody knows them, except myself. There's one—that girl over there dancing with that middle-aged man who has mail sent here but doesn't live here. Could they be of use?"

"Just the thing," exclaimed Craig enthusiastically. "Can't you have her get acquainted—just as a precaution—with that man? His name, by the way, I understand is Sherburne."

"I'll do it," agreed Dunn, rising unostentatiously.

Just then I happened to glance across the floor and over the heads of those seated at the tables at a door opposite us. It was my turn hastily to seize Kennedy's elbow.

"Good God!" I exclaimed involuntarily.

There, in the further doorway of the tea room, stood Judson Seabury himself!

Without a word, Craig rose and quickly crossed the dancing floor, stopping before Mrs. Seabury's table. Instead of waiting to be introduced, he sat down deliberately, as though he had been there all the time and had just gone out of the room and come back. He did it all so quickly that he was able in a perfectly natural way to turn and see that Seabury himself had been watching and now was advancing slowly, picking his way among the crowded tables.

From around my corner I saw Craig whisper a word or two to Mrs. Seabury, then rise and meet Seabury less than halfway from the door by which he had been standing.

The tension of the situation was too much for Mrs. Seabury. Confounded and bewildered, she fled precipitately, passing within a few feet of my table. Her face was positively ghastly.

As for Sherburne, he merely sat a moment and surveyed the irate husband with calm and studied insolence at a safe distance. Then he, too, rose and turned deliberately on his heel.

Curious to know how Craig would meet the dilemma, I watched eagerly and was surprised to see Seabury, after a moment's whispered talk, turn and leave the tea room by the same door through which he had entered.

"What did you do?" I asked, as Craig rejoined me a few moments later. "What did you say? My hat's off to you," I added in admiration.

"Told him I had trailed her here with one of my operatives, but was convinced there was nothing wrong, after all," he returned.

"You mean," I asked as the result of Craig's quick thinking dawned on me, "that you told him Sherburne was your operative?"

Kennedy nodded. "I want to see him, now, if I can," he said simply.