“Certainly,” said Carden uneasily, “but how are we going to accomplish it by to-morrow?  How is it going to be accomplished at all?”

The Tracer of Lost Persons rose and began to pace the long rug, clasping his hands behind his back.  Minute after minute sped; Carden stared alternately at Mr. Keen and at the blue sky through the open window.

“It is seldom,” said Mr. Keen with evident annoyance, “that I personally take any spectacular part in the actual and concrete demonstrations necessary to a successful conclusion of a client’s case.  But I’ve got to do it this time.”

He went to a cupboard, picked out a gray wig and gray side whiskers and deliberately waved them at Carden.

“You see what these look like?” he demanded.

“Y-yes.”

“Very well.  It is now noon.  Do you know the Park?  Do you happen to recollect a shady turn in the path after you cross the bridge over the swan lake?  Here; I’ll draw it for you.  Now, here is the lake; here’s the esplanade and fountain, you see.  Here’s the path.  You follow it—­so!—­around the lake, across the bridge, then following the lake to the right—­so!—­then up the wooded slope to the left—­so!  Now, here is a bench.  I mark it Number One. She sits there with her book—­there she is!”

“If she looks like that—­” began Carden.  And they both laughed with the slightest trace of excitement.

“Here is Bench Number Two!” resumed the Tracer.  “Here you sit—­and there you are!”

[Illustration:  MR. KEEN’S SKETCH OF THE RENDEZVOUS]

“Thanks,” said Carden, laughing again.

“Now,” continued the Tracer, “you must be there at one o’clock.  She will be there at one-thirty, or earlier perhaps.  A little later I will become benignly visible.  Your part is merely a thinking part; you are to do nothing, say nothing, unless spoken to.  And when you are spoken to you are to acquiesce in whatever anybody says to you, and you are to do whatever anybody requests you to do.  And, above all, don’t be surprised at anything that may happen.  You’ll be nervous enough; I expect that.  You’ll probably color up and flush and fidget; I expect that; I count on that.  But don’t lose your nerve entirely; and don’t think of attempting to escape.”

“Escape!  From what?  From whom?”

“From her.”

“Her?”

“Are you going to follow my instructions?” demanded the Tracer of Lost Persons.

“I—­y-yes, of course.”

“Very well, then, I am going to rub some of this under your eyes.”  And Mr. Keen produced a make-up box and, walking over to Carden, calmly darkened the skin under his eyes.

“I look as though I had been on a bat!” exclaimed Carden, surveying himself in a mirror.  “Do you think any girl could find any attraction in such a countenance?”

“She will,” observed the Tracer meaningly.  “Now, Mr. Carden, one last word:  The moment you find yourself in love with her, and the first moment you have the chance to do so decently, make love to her.  She won’t dismiss you; she will repulse you, of course, but she won’t let you go.  I know what I am saying; all I ask of you is to promise on your honor to carry out these instructions.  Do you promise?”