Toward the Park side they advance, one leaning heavily upon the other.  Shirley, his broad shoulders hunched up; with the collar drawn high about his neck, the murderous looking cap down over his eyes, followed them doggedly.

A big limousine was speeding down the Avenue from some homing theater party.  Shirley hailed it with an authoritive yell which caused the chauffeur to put on a quick brake.

“Git out dere,—­no gun play.  Up inter dat car!” he added, as they approached the machine.

“Say, what you drivin’ at?” cried the driver, queruously.  “Is this a hold-up?” It was a puzzling moment, but the criminologist’s calm bravado saved the situation:  as luck would have it no policemen were in sight, to spoil the maneuver.

“No,” and he assumed a more natural voice and dialect.  “I’m a detective.  These men were just house-breaking, and I got them.  There’s twenty-five dollars in it for you, if you take us down to the Holland Detective Agency, in ten minutes.”

“He’s kiddin’ ye, feller,” snapped out one man.

“Don’t fall fen him, yen boob!” sung out the other.

But Shirley’s automatic now appeared outside the coat pocket.  The chauffeur realized that here was serious gaming.  With his left hand Shirley jerked out the ever ready police card and fire badge, which seemed official enough to satisfy the driver.

“Quick now, or I’ll run you in, too, for refusing to obey an officer.  You men climb into that back seat.  Driver, beat it now to Thirty-nine West Forty Street, if you need that twenty-five dollars.  I’ll sit with them.  I don’t want any interference so I can come back and nab the rest of their gang.”

His authoritative manner convinced this new ally, and he climbed into the car, facing his prisoners, with the two weapons held down below the level of the windows.  Pedestrians and other motorists little recked what strange cargo was borne as the car raced down the broad thoroughfare.

In nine minutes they drew up before the Holland Agency, a darkened, brown front house of ancient architecture.  The chauffeur sprang out to swing back the door.

“Go up the steps, and tell the doorman that Captain Cronin wants two men to bring down their guns and handcuffs and get two prisoners.  Quick!”

The street was not empty, even at this hour.  Yet the passersby did not realize the grim drama enacted inside the waiting machine.  Hours seemed to pass before Cronin’s men returned with the driver, as much surprised by the three strange faces within the machine, as he had been.

“You take these men upstairs and keep them locked up,” bluntly commanded the criminologist.  “They’re nabbed on the new case of the Captain’s which started to-night, I’m going over to Bellevue to see him.”  His voice was still disguised, his features twisted even yet.

The men gave him a curious glance, and then obeyed.  As they disappeared behind the heavy wooden door, Shirley stepped into a dark hallway, close by.  He lit a wax match to give him light for the choosing of the right amount, from the roll of bills which he drew forth.  The chauffeur whistled with surprise at the size of the denominations.  The twenty-five were handed over.