"Fists would be enough," muttered Tom, as with the others he prepared to follow their leader.

Like so many ghosts they drifted out of the hallway, and, moving in the shadow of the houses, though in the rain and darkness that seemed almost unnecessary, they stealthily approached the entrance to the alley.

It was in one of the poorer sections of the town, and the dwelling houses were interspersed with factories and coal yards. On each side of the alley stood the wall of a factory, three stories in height. No light came from any window, and the alley itself was as dark as pitch.

"Bart and I will stand on this side, and you two fellows take the other side," whispered Frank, when they reached the mouth of the alley. "Keep right on your toes and be ready to nab those fellows when they come out."

The others did as directed and all waited, tense with expectation, their clubs ready for instant service if resistance should be offered.

The rain kept pouring down in torrents, and as it fell, a glaze formed on the sidewalks, so that it was with difficulty that the Army Boys kept their feet.

They were eager to bring the matter to a head, and the waiting in drenching rain wore on their patience.

"Could they have possibly gone out some other way, leaving us here to hold the bag?" queried Bart Raymond, after five minutes had passed without result.

"I don't think so," returned Frank. "I'm dead sure there isn't any way to get out except the way they went in. They're in there holding a pow-wow of some kind."

Ten minutes more passed, and by that time even Frank had begun to have doubts. Tom slipped over to him from the other side of the alley.

"For the love of Mike! let's get a move on and go into the alley and smoke them out," he whispered. "We can get them there just as well as here."

"Just five minutes more," Frank replied. "They may hear us going in and be on their guard, while if we nab them here we'll catch them unawares. But if they're not out in that time, we'll go in and round them up."

At the end of the stipulated time Frank gave the signal.

"Creep in as softly as you can," he admonished his comrades. "Spread across so that they can't slip between us. They've got to be somewhere between us and that brick wall at the back."

Moving with all the caution that their experience as scouts had taught them in their frequent incursions into No Man's Land during the war, the four Army Boys crept noiselessly into the darkness of the alley.

Ten, twenty, thirty feet, and still no sign of their quarry. They must be close to them now.

On they went, wonder gradually giving way to doubt, until with a muttered exclamation Frank came plump up against the wall that marked the alley's end.

"Stung!" he murmured in profound disgust.

His comrades gathered close about him.

"That's one on us," muttered Tom.

"We're done good and proper," agreed Billy.

"Are you dead sure that you saw them come in?" queried Bart of Frank.

"I know I did," replied Frank, who although puzzled was not shaken in his conviction.

"They must have been ghosts then," gibed Tom. "Nothing else could have vanished through a brick wall."

Frank drew his flashlight from his pocket and flashed it about. There was no one to be seen.

"That wall is perfectly blank," he murmured in perplexity. "Thirty feet high if it's an inch. There isn't an opening in it anywhere."

"Could they have got into the windows of the building on either side?" suggested Bart.

Frank swept the flashlight on the walls of the factories.

"Not a chance," he affirmed. "All these windows are protected with iron bars and nothing could get between them. Those fellows seem to have just melted away."

At that instant a report rang out, and the flashlight was knocked from his hand by a bullet.

"Down, fellows!" he shouted, setting the example, and the next