s something out of the ordinary here, that's certain."

Keeping well in the gloom of the block of dwellings near by, Nick
retraced his steps to the corner, then crossed the street and presently
approached a paved driveway leading to a small stable at the rear of the
suspected house.

The high gate, composed of sharp iron pickets, was securely closed and
locked; so Nick returned to an alley which he had just passed, and which
ran back of a block of dwellings fronting on the avenue where he had
left the cab.

Stealing into the alley, Nick quickly scaled the high, wooden fence,
crossed two adjoining back yards, and thus reached a wall near the
stable mentioned.

To mount the wall and drop back of the stable was equally feasible, and
Nick then had the rear of Cervera's dwelling plainly in view.

Then his searching gaze was rewarded. One of the rear rooms was brightly
lighted, with only the lace draperies at the two windows preventing
observation from outside.

"Evidently a rear sitting room, or library," thought Nick, calculating
the arrangement of the house. "I will at least learn who is in there."

He listened briefly for any sound in or about the stable, then stole
quickly across the gloomy, paved yard and approached the house.

The windows of the lighted room were two feet or more above his head;
but having reached a position just below one of them, he sprang up and
seized the stone coping outside, and drew himself up to peer into the
room.

Then, just as his head rose into the glow of light from within, clearly
revealing his location, Nick heard a sound the deadly nature of which he
instantly recognized.

Ping!

It was the short, sharp, peculiar song of a flying bullet--once heard,
always remembered.

Then came the dull thud when the leaden ball beat itself shapeless
against the stone wall beside him.

The bullet had passed within an inch of Nick's ribs, and he knew at once
that he was now a mark for hidden foes.

Yet there had been no revolver report to suggest their location, and
Nick instantly surmised that the ball must have been discharged with an
air gun.

He knew that it must have come from some quarter behind him, however.
And he knew, too, how to bring his murderous assailants from their
secret cover.

As quick as a flash, the instant the ball smote the wall beside him,
Nick let go his hold upon the stone coping and dropped into the darkness
below the window, falling prostrate upon his ba