"Yah, on der next street."

"I see. Well, I guess I won't wait for the man."

Hal walked back slowly, and passed the house. What should he do next?
Would it be worth while to track Allen farther at present?

Suddenly an idea popped into his mind. Farther up the street he had
passed a costumers' establishment, where everything in the shape of a
make-up for detective or actor was to be had.

He walked back to the place, and entered it. Back of the counter stood a
young who came up and asked what was wished.

"Can I get a small, black mustache cheap?" asked Hal.

"We have them for twenty-five cents."

"Will they stay on?"

"Yes, if you adjust them properly."

"Then let me have one."

The clerk brought forth the false mustache, and helped Hal to put it on.
The youth looked in a mirror at the effect.

"Changes me completely," he said.

"It does, sir. Makes you look five years older, too."

"Here is your money."

The clerk took Hal's quarter, and the boy walked forth from the place
without taking the trouble to remove the mustache. Once outside he could
not help but laugh.

"I am certainly going into the detective business, and no mistake," he
thought. "I trust I am successful in what I undertake to do."

Hal walked back toward the gambling-house, and after some hesitation
ascended the stone steps and rang the bell.

A negro answered his summons.

"Is Mr. Arnold here?" asked the lad, as coolly as he could.

"Mr. Arnold?" The negro shook his head.

"But he must be," persisted Hal. "He said he was coming here."

"Don't t'ink I see him, sah. What kind ob a lookin' gen'men he is?"

"About medium built, with a dark mustache," replied Hal. "I have
important news for him. He said he was going to try his luck here
to-night."

"I see, sah. Den you knows dis place, sah."

"Oh, yes!"

"Come in, sah."

Hal entered, and the door was closed and locked behind him.

"Now you kin go upstairs an' see if de gen'men am here," said the negro.
"He might be, yo' know, an' I not know his name, sah."

"All right; I'll take a look around," replied Hal.

CHAPTER XXI.

IN A DANGEROUS PLACE.

Hal felt that his situation was a delicate one, and that he must go
slow. Were it discovered that he had entered the den of vice merely for
the purpose of spying, it might go hard with him.

The negro waved his hand toward the thickly carpeted stairway, and Hal
ascended to the second floor of the mansion.

He looke