door opened and closed, and he was gone.

At the end of an hour he returned, passed on through to the
diplomatist's private office, sat down in front of the locked safe
again, and set the dial at thirty-six. Senor Rodriguez looked on,
astonished, as Mr. Grimm pressed the soft rubber sounder of a
stethoscope against the safe door and began turning the dial back toward
ten, slowly, slowly. Thirty-five minutes later the lock clicked. Mr.
Grimm rose, turned the handle, and pulled the safe door open.

"That's how it was done," he explained to the amazed diplomatist. "And
now, please, have a servant hand my card to Miss Thorne."

XI

THE LACE HANDKERCHIEF

Still wearing the graceful, filmy morning gown, with an added touch, of
scarlet in her hair--a single red rose--Miss Thorne came into the
drawing-room where Mr. Grimm sat waiting. There was curiosity in her
manner, thinly veiled, but the haunting smile still lingered about her
lips. Mr. Grimm bowed low, and placed a chair for her, after which he
stood for a time staring down at one slim, white hand at rest on the arm
of the seat. At last, he, too, sat down.

"I believe," he said slowly, without preliminaries, "this is your
handkerchief?"

He offered the lacy trifle, odd in design, unique in workmanship,
obviously of foreign texture, and she accepted it.

"Yes," she agreed readily, "I must have dropped it again."

"That is the one handed to you by Senor Rodriguez," Mr. Grimm told her.
"I think you said you lost it in his office yesterday afternoon?"

"Yes?" She nodded inquiringly.

"It may interest you to know that Senor Rodriguez's butler positively
identifies it as one he restored to you twice at dinner last evening,
between seven and nine o'clock," Mr. Grimm went on dispassionately.

"Indeed!" exclaimed Miss Thorne.

"The senor identifies it as one he found this morning in his office,"
Mr. Grimm explained obligingly. "During the night fifty thousand dollars
in gold were stolen from his safe."

There was not the slightest change of expression in her face; the
blue-gray eyes were still inquiring in their gaze, the white hands still
at rest, the scarlet lips still curled slightly, an echo of a smile.

"No force was used in opening the safe," Mr. Grimm resumed. "It was
unlocked. It's an old model and I have demonstrated how it could have
been opened either with the assistance of a stethoscope, which catches
the sound of the tumbler in the lock, or by