Watch him; observe everything he does.

If he should recognize you and speak to you, be as amiable to him as though it were not by my orders." "Then--then I _am_ to be a detective!" she faltered.
The Tracer did not appear to hear her.

He took up the notes, turned to the telephone, and began to send out a general alarm, reading the description of the person whom Gatewood had described.

The vast, intricate and delicate machinery under his control was being set in motion all over the Union.
"Not that I expect to find her outside the borough of Manhattan," he said, smiling, as he hung up the receiver and turned to her; "but it's as well to know how many types of that species exist in this Republic, and who they are--in case any other young man comes here raving of brown eyes and 'gleams' in the hair." Miss Southerland, to her own intense consternation, blushed.
"I think you had better order that habit at once," said the Tracer carelessly.
"Tell me, Mr.Keen," she asked tremulously, "am I to spy upon Mr.
Gatewood?
And report to you?
.

.