a
wonderful brilliant, some three hundred carats--perfect in its blazing
crystalline orange beauty. There it lay, a jewel which might charm and
arouse the cupidity of two hemispheres. It shone like a thing of life.
Yet back of its orange fire lay a black tragedy.

Margot was on his feet instantly.

"That is not the--"

"Just a moment, Mr. Margot," interrupted Kennedy. "I think Mr. Wade will
be able to show that it is the Invincible when he matches up the parts
that have been hurriedly cut from--from the wonderful Arkansas diamond,"
Craig added sarcastically. "Miss Hoffman, Dr. Preston tells us that
before you were a diamond saleswoman you had been a trained nurse!"

The look Elsa Hoffman flashed, as her calm exterior refused to conceal
her emotions longer, was venomous.

Kennedy was the calmest one of us all as he tapped the little
galvanometer significantly with his index finger.

"De Guerre," he exclaimed, leaning forward slightly, "you and your
lover, Elsa Hoffman, planned cunningly to rob your own brothers. But,
instead of robbers merely," he ground out, "you are murderers!"

CHAPTER X

THE SIXTH SENSE

"I suppose you have read in the papers of the mysterious burning of our
country house at Oceanhurst, on the south shore of Long Island?"

It had been about the middle of the afternoon that a huge automobile of
the latest design drew up at Kennedy's laboratory and a stylishly
dressed woman, accompanied by a very attentive young man, alighted.

They had entered and the man, with a deep bow, presented two cards
bearing the names of the Count and Countess Alessandro Rovigno.

Julia Rovigno, I knew, was the daughter of Roger Gaskell, the retired
banker. She had recently married Count Rovigno, a young foreigner whose
family had large shipping interests in America and at Trieste in the
Adriatic.

"Yes, indeed, I have read about it," nodded Craig.

"You see," she hurried on a little nervously, "it was a wedding present
to us from my father."

"Giulia," put in the young man quickly, giving her name an accent that
was not, however, quite Italian, "thinks the fire was started by an
incendiary."

Rovigno was a tall, rather boyish-looking man of thirty-two or
thirty-three, with light brown hair, light brown beard and mustache. His
eyes and forehead spoke of intelligence, but I had never heard that he
cared much about practical business affairs. In fact, to American
society Rovigno was known chiefly a