upon?"

At Forty-second Street he took the elevated road, and in twenty minutes
he was at his office. Here he found the spy who had followed Mr. Mitchel
to Philadelphia.

"Well," said he, angrily, "what are you doing here?"

"I am sure that Mitchel has returned to New York. I came on hoping to
catch up with him, and at least to warn you."

"Your warning comes too late. The mischief is done. Didn't you have
brains enough to telegraph?"

"I did just before I started." The despatch was on Mr. Barnes's desk
unopened. It had arrived after he had started for the festival.

"Well, well," said the detective, testily, "I suppose you have done your
best. That fellow has the devil's luck. What made you think that he had
come to New York? Wasn't he sick?"

"I thought that might be a game for an _alibi_. To find out, I
registered, asking for a room near my friend Mr. Mitchel. They gave me
the one next to his. I picked the lock of the door between the rooms and
peeped in. Seeing no one, I went in. The place was empty. The bird had
skipped."

"Take the next train back to Philadelphia, and do the best you can to
find out when Mitchel reaches there. He has gone back sure, and will be
sick in bed in the morning, or my name is not Barnes. Bring me proof of
his trip to and from New York, and I will give you fifty dollars. Skip."

CHAPTER XI.

MR. BARNES RECEIVES SEVERAL LETTERS.

On the morning of the third of January the mail which reached Mr. Barnes
contained several letters of interest to those who follow this history.
The first which he opened was very brief. It read:

"If Mr. Barnes will call at his earliest convenience he will
greatly oblige EMILY REMSEN."

He read this twice, and then took up another, which was as follows:

"J. BARNES, ESQ.:

"DEAR SIR: I take the liberty of recalling to your mind the
conversation which I had with you last month. I regret very much
that I should have hinted that there was any possibility that my
friend Mr. Mitchel might be implicated in the Pullman car robbery.
As you know, Miss Emily Remsen was robbed at the festival, night
before last, of a ruby pin worth $20,000. It is very evident to my
mind that Mr. Mitchel's hand is in this. I know that he pretends to
be sick at a hotel in Philadelphia, but may not that be a humbug?
It would have been easy enough for him to slip over, don one of the
Forty T