rifle
might be used to hold a twenty-two caliber bullet. It would not take
the rifling of this."

Drew shook his head. "That's hardly possible," he declared. "It's too
vague and doesn't suit me. We're going to find that the deeper we get
in this thing, the simpler will be the explanation. I remember any
number of cases which have been solved in this city where the mystery
was so wrapped up in speculation and the improbable that our minds
failed to grasp the simple thing which was the solution."

"Then you think the lack of rifling on the bullet might be the opening
wedge to catching the man who shot Stockbridge?"

"It could well be, Fosdick. The lack of a thing sometimes is just as
important as the visible clue. Do you remember the Rajah case at
Gramercy Park?"

Fosdick leaned back in his chair and stared up at the ceiling. "Seems
to me that I do," he said, thrusting out his lower lip. "There was a
big jewel missing. Sort of an Idol's Eye case--wasn't it?"

"Exactly! A white diamond was missing at a dinner. Lights went out as
they were passing the stone around the table. Lights came on again and
the diamond was gone. Everybody accused. A strange print was found on
the sideboard. Servants knew nothing about it. The print didn't
correspond to any which we took there. Seemed impossible and all that.
Well, the very fact that the print didn't correspond was the means of
finding the stone and the culprit. You remember it?"

"Vaguely."

"Simple! A Lascar who waited on the table slipped off his shoes, crept
into the room, secured the diamond and climbed to the sideboard where
he hid it on top of a picture. The thumbprint which we puzzled our
heads over was a toe-print! We got the fellow!"

"I recall it now," said Fosdick. "I think one of our men thought out
the matter."

"He didn't!" declared the detective. "We worked it out! The city
department had given up the case. This may be the same. I'll venture to
say that as soon as you get a good operative some private agency
secures his services. Now, Commissioner, confess up. What manner of gun
could fire a bullet, such as a cupronickel one, without leaving
markings?"

"Smooth bore. An old flint-lock--for instance."

"We'll grant that! They're clumsy, however. The shot which killed the
millionaire was fired at very close range through a smooth tube of a
greater caliber than the diameter of the bullet found in his head. If
it were fired through a gun which was rifled,