Indeed, before he had fairly reached the road, these nostrils had telegraphed to his brain an odor that not only was highly interesting, but totally new to him.

Lad's experience with scents was far-reaching.

But this smell lay totally outside all his knowledge or memory.
It was a rank and queer smell;--not strong enough, out there in the open, to register in a human-brain; but almost stingingly acute to the highly sensitized dog.

It was an alluring scent; the sort of odor that roused all his curiosity and seemed to call for prompt investigation.
Nose to ground, Lad set off to trace the smell to its source.

Strong as it was, it grew stronger and fresher at every step.