“Cops!” he panted.

Joe looked, and he saw two helmeted policemen approaching, with bright stars shining on their breasts.

“Let ’s get out of this,” he whispered to Fred and Charley.

The gang had already taken to flight, and they blocked the boys’ retreat in one quarter, and in another they saw the policemen advancing.  So they took to their heels in the direction of Brick Simpson’s slip, the policemen hot after them and yelling bravely for them to halt.

But young feet are nimble, and young feet when frightened become something more than nimble, and the boys were first over the fence and plunging wildly through a maze of back yards.  They soon found that the policemen were discreet.  Evidently they had had experiences in slips, and they were satisfied to give over the chase at the first fence.

No street-lamps shed their light here, and the boys blundered along through the blackness with their hearts in their mouths.  In one yard, filled with mountains of crates and fruit-boxes, they were lost for a quarter of an hour.  Feel and quest about as they would, they encountered nothing but endless heaps of boxes.  From this wilderness they finally emerged by way of a shed roof, only to fall into another yard, cumbered with countless empty chicken-coops.

Farther on they came upon the contrivance which had soaked Brick Simpson’s pursuers with water.  It was a cunning arrangement.  Where the slip led through a fence with a board missing, a long slat was so arranged that the ignorant wayfarer could not fail to strike against it.  This slat was the spring of the trap.  A light touch upon it was sufficient to disconnect a heavy stone from a barrel perched overhead and nicely balanced.  The disconnecting of the stone permitted the barrel to turn over and spill its contents on the one beneath who touched the slat.

The boys examined the arrangement with keen appreciation.  Luckily for them, the barrel was overturned, or they too would have received a ducking, for Joe, who was in advance, had blundered against the slat.

“I wonder if this is Simpson’s back yard?” he queried softly.

“It must be,” Fred concluded, “or else the back yard of some member of his gang.”

Charley put his hands warningly on both their arms.

“Hist!  What ’s that?” he whispered.

They crouched down on the ground.  Not far away was the sound of some one moving about.  Then they heard a noise of falling water, as from a faucet into a bucket.  This was followed by steps boldly approaching.  They crouched lower, breathless with apprehension.

A dark form passed by within arm’s reach and mounted on a box to the fence.  It was Brick himself, resetting the trap.  They heard him arrange the slat and stone, then right the barrel and empty into it a couple of buckets of water.  As he came down from the box to go after more water, Joe sprang upon him, tripped him up, and held him to the ground.