Birnes.

He quickened his pace a little, then slowed up instantly, because Mr.
Wynne had stopped on the corner of Madison Avenue, and as a downtown
car came rushing along he stepped out to board it. Mr. Birnes
scuttled across the street, and by a dexterous jump swung on the car
as it fled past. Mr. Wynne had gone forward and was taking a seat;
Mr. Birnes remained on the back platform, sheltered by the
accommodating bulk of a fat man, and flattered himself that Mr.
Wynne had not seen him. By peering over a huge shoulder the
detective was still able to watch Mr. Wynne.

He saw him pay his fare, and then he saw him place the small
sole-leather grip on his knees and unfasten the catch. Not knowing
what was in that grip Mr. Birnes was curious to see what came out of
it. Nothing came out of it--it was empty! There was no question of
this, for Mr. Wynne opened it wide and turned it upside down to shake
it out. It didn't mean anything in particular to Mr. Birnes, the fact
that the grip was empty, so he didn't get excited about it.

Mr. Wynne left the car at Thirty-fourth Street, the south end of the
Park Avenue tunnel, by the front door, and the detective stepped off
the rear end. Mr. Wynne brushed past him as he went up the stairs,
and as he did so he smiled a little--a very little. He walked on up
Park Avenue to Thirty-seventh Street, turned in there and entered a
house about the middle of the block, with a latch-key. The detective
glanced at the number of the house, and felt aggrieved--it was the
number that was written in the note! And Mr. Wynne had entered with
a key! Which meant, in all probability, that he _did_ live there, as
he had said!