He had first flattened the edge of the envelope, then roughened it, and finally slit it open.

“Scientific letter-opening,” he remarked, as he pulled out a little note written on the hotel paper.  It read: 

Dear Harry: 

Called you up twice and then dropped into the hotel, but you seem to be out all the time.  Have something very important to tell you.  Shall be busy to-night and in the morning, but will be at the the dansant at the Futurist Tea Room to-morrow afternoon about four.  Be sure to be there.

        Marie.

“I shall,” commented Kennedy.  “Now the question is, how to seal up this letter so that he won’t know it has been opened.  I saw some of this very strong mucilage in the office.  Ring the bell, Walter.  I’ll get that impervious waiter to borrow it for a moment.”

Five minutes later he had applied a hair line of the strong, colourless gum to the inside of the envelope and had united the edges under pressure between the two pieces of wood.  As soon as it was dry he excused himself again and went back to the office, where he managed to secure an opportunity to stick the letter back in the box and chat for a few minutes longer with the Titian.

“There’s a wild cabaret down in the main dining-room,” he reported on his return.  “I think we might just as well have a glimpse of it before we go.”

Kennedy paid the cheque, which by this time had mounted like a taximeter running wild, and we drifted into the dining-room, a rather attractive hall, panelled in Flemish oak with artificial flowers and leaves about, and here and there a little bird concealed in a cage in the paper foliage.

As cabarets go, it was not bad, although I could imagine how wild it might become in the evening or on special occasion.

“That Dr. Harris interests me,” remarked Kennedy across the table at us.  “We must get something in writing from him in some way.  And then there’s that girl in the office, too.  She seems to be right in with all these people here.”

Evidently the cabaret had little of interest to Miss Kendall, who, after a glance that took in the whole dining-room and disclosed none there in the gay crowd who, as far as we could see, had any relation to the case, seemed bored.

Craig noticed it and at once rose to go.

As we passed out and into the corridor, Miss Kendall turned and whispered, “Look over at the desk—­Dr. Harris.”

Sure enough, chatting with the stenographer was a man with one of those black bags which doctors carry.  He was a young man in appearance, one of those whom one sees in the White Light District, with unnaturally bright eyes which speak of late hours and a fast pace.  He wore a flower in his buttonhole—­a very fetching touch with some women.  Debonair, dapper, dashing, his face was not one readily forgotten.  As we passed hurriedly I observed that he had torn open the note and had thrown the envelope, unsuspectingly, into the basket.