The cab which had been drifting along behind him immediately came up.
"Now, Jimmy, get on the job," instructed Mr.Birnes, as he stepped in.

"Keep that chap in sight and when he stops you stop." Mr.Wynne's cab jogged along comfortably up the avenue, twisting and winding a path between the other vehicles, the while Mr.Birnes regarded it with thoughtful gaze.

Its number dangled on a white board in the rear; Mr.Birnes just happened to note it.
"Grand Central Station, I'll bet a hat," he mused.
But the closed cab didn't turn into Forty-second Street; it went past, then on past Delmonico's, past the Cathedral, past the Plaza, at Fifty-ninth Street, and still on uptown.

It was not hurrying-- it merely moved steadily; but once free of the snarl which culminates at the Fifty-ninth Street entrance to Central Park, its speed was increased a little.

Past Sixty-fourth Street, Sixty-fifth, Sixty-sixth, and at Sixty-seventh it slowed up and halted at the sidewalk on the far side.
"Stop in front of a door, Jimmy," directed the detective hastily.
Jimmy obeyed gracefully, and Mr.Birnes stepped out, hardly half a block behind the closed cab.