se in the cab, which he had had
in waiting, with all the properties for effecting the change mentioned.

That Patsy would constantly keep their quarry in view, and without being
suspected, Nick had not a doubt. Nor was he mistaken. At the end of
twenty minutes the clever young driver slowed down upon approaching an
uptown corner, and signaled Nick to get out.

The detective alighted from the door on the side from which he had
received the signal, yet the cab did not stop. Nick trotted along beside
the vehicle for a rod or two, keeping it between him and the side street
into which Patsy quickly signed that the hack had turned.

"Fourth house on the right," he softly cried. "I saw them pull up at it
just as I reached the corner, so I kept right on up the avenue. They've
not gone in yet."

"Good enough," replied Nick, approvingly. "Take home the traps I have
left in the cab."

"Sure thing. You don't want any help to-night against this push, do
you?"

"No, indeed. There'll be but little doing to-night, I imagine. Remember
the house, however, in case I fail to show up."

"You may gamble on that, sir. I have it down pat."

They had now passed the upper corner of the side street, and Nick felt
sure that he had not been seen leaving the cab. He darted quickly back
of the vehicle and gained the sidewalk, then stole back and peered
around the corner.

Cervera and her companion were just mounting the steps of an imposing
stone residence, entirely separate from its neighbors, and their
carriage was driving rapidly away.

Nick waited until the couple had entered the house, then he crossed to
the gloom of a doorway on the opposite side and had a look at the
dwelling.

From basement to roof there was no sign of a light. Even the hall
appeared to be in darkness, and Nick waited and watched for several
minutes, expecting to see at least one of the rooms lighted.

Not a glimmer or gleam, however, appeared from any quarter.

"H'm!" he presently muttered, a little perplexed. "Either they are
remaining in darkness, or else they have all of those windows heavily
curtained. If the latter is the case, I must discover for what reason.

"Possibly they are entirely alone in there, and have gone to some room
at the rear of the house. Or maybe they have suspected an espionage, and
are now watching from the gloom of one of those front windows. I'll fool
them if that is so, and will also have a look at the rear of the house.
There i