He hung up the receiver with a mingled air of gratification and exasperation, I fancied.

“Haven’t you fellows finished yet?” he asked finally, coming over to us, a little brusquely.

“Just about,” returned Kennedy, who had by this time begun slowly to dismember and pack up the dynamometer, determined to take advantage of every minute both to observe Langhorne and to fix in his mind the general lay-out of the office.

“Everybody seems to be interested in me this morning,” he observed, for the moment forgetting the embargo he had imposed on his own words.

As for myself, I saw at once that others besides ourselves were keenly interested in this robbery.

“There,” remarked Kennedy when at last he had finished packing up the dynamometer into two packages.  “At least, Mr. Langhorne, you have the satisfaction of knowing that it was in all probability a man, a strong man, and one experienced in forcing doors who succeeded in entering your office during your brief absence last night”

Langhorne shrugged his shoulders non-committally, but it was evident that he was greatly relieved and he could not conceal his interest in what Kennedy was doing, even though he had succeeded in conveying the impression that it was a matter of indifference to him.

“I suppose you keep a great many of your valuable papers in safety deposit vaults,” ventured Kennedy, finishing up the wrapping of the two packages, “as well as your personal papers perhaps at home.”

He made the remark in a casual manner, but Langhorne was too keen to fall into the trap.

“Really,” he said with an air of finality, “I must decline to be interviewed at present.  Good-day, gentlemen.”

“A slippery customer,” was Craig’s comment when we reached the street outside the office.  “By the way, evidently Mrs. Ogleby is leaving no stone unturned in her effort to locate that Black Book and protect herself.”

I said nothing.  Langhorne’s manner, self-confident to the point of bravado, had baffled me.  I began to feel that even if he had lost the detectaphone record, his was the nature to carry out the bluff of still having it, in much the same manner that he would have played the market on a shoestring or made the most of an unfilled four-card flush in a game of poker.

Kennedy was far from being discouraged, however.  Indeed, it seemed as if he really enjoyed matching his wit against the subtlety of a man like Langhorne, even more than against one the type of Dorgan and Murtha.

“I want to see Carton and I don’t want to carry these bundles all over the city,” he remarked, changing the subject for the moment, as he turned into a public pay station.  “I’ll ring him up and have him meet us at the laboratory, if I can.”

A moment later he emerged, excited, perspiring from the closeness of the telephone booth.

“Carton has some news—­a letter—­that’s all he would say,” he exclaimed.  “He’ll meet us at the laboratory.”