He put the bit of lace into his coat and went on with the search:

Three American Beauty roses, somewhat crushed and broken, were in the
far corner. From certain abrasions in the stems, he concluded that they
had been torn, or loosed, from a woman's corsage.

He felt again--then he struck a match, leaning well inside the cab so
as to hide the light as much as possible.

The momentary flare disclosed a square envelope standing on edge and
close in against the seat. Extinguishing the match, he caught it up.

It was of white linen of superior quality, without superscription, and
sealed; the contents were very light--a single sheet of paper, likely.

The handkerchief, the crushed roses, the unaddressed, sealed
envelope--the horse, the empty and deserted cab, standing before a
vacant lot, at one o'clock in the morning! Surely any one of them was
enough to stir the imagination; together they were a tantalizing
mystery, calling for solution and beckoning one on.

Harleston took another look around, saw no one, and calmly pocketed the
envelope. Then, after noting the number of the cab, No. 333, he gathered
up the lines, whipped the ends about the box, and chirped to the horse
to proceed.

The horse promptly obeyed; turned west on Massachusetts Avenue, and
backed up to his accustomed stand in Dupont Circle as neatly as though
his driver were directing him.