As he worked, I could not believe that it was wholly fancy that
caused me to think of him as searching with dilated nostrils, like
a scientific human bloodhound. For, it was not long before I began
to realize what he was looking for in the marks of cars left on
the oiled roadway.

During perhaps half an hour he continued studying the road, above
and below the exact point of the accident. At length a low
exclamation from him brought me to his side. He had dropped down
in the grease, regardless of his knees and was peering at some
rather deep imprints in the surface dressing. There, for a few
feet, were plainly the marks of the outside tires of a car, still
unobliterated.

Garrick had pulled out copies of the photographs he had made of
the tire marks that had been left at the scene of the finding of
the unfortunate Rena Taylor's body, and was busy comparing them
with the marks that were before him.

"Of course," Garrick muttered to me, "if the anti-skid marks of
the tires were different, it would have proved nothing, just as in
the other case where we looked for the tire prints. But here, too,
a glance shows that at least it is the same make of tires."

He continued his comparison. It did not take me long to surmise
what he was doing. He was taking the two sets of marks and, inch
by inch, going over them, checking up the little round metal
insertions that were placed in this style of tire to give it a
firmer grip.