left in the dust and grease of an asphalted street or the mud of
a road. It had never occurred to me that they might be used in
any way. Yet here Craig was, calmly tracing out the similarity
before my very eyes, identifying the marks made in the photograph
with the prints left on the bits of paper.

As I followed him, I had a most curious feeling of admiration for
his genius. "Craig," I cried, "that's the thumb-print of an
automobile."

"There speaks the yellow journalist," he answered merrily.
"'Thumb Print System Applied to Motor Cars'--I can see the Sunday
feature story you have in your mind with that headline already.
Yes, Walter, that's precisely what this is. The Berlin police
have used it a number of times with the most startling results."

"But, Craig," I exclaimed suddenly, "the paper prints, where did
you get them? What machine is it?"

"It's one not very far from here," he answered sententiously, and
I saw he would say nothing more that might fix a false suspicion
on anyone. Still, my curiosity was so great that if there had
been an opportunity I certainly should have tried out his plan on
all the cars in the Fletcher garage.

Kennedy would say nothing more, and we ate our luncheon in
silence. Fletcher, who had decided to lunch with the Greenes,
called Kennedy up on the telephone to tell him it would be all
right for him to call on Miss Bond later in the afternoon.