At the same time the clue to its whereabouts would lie in a certain principle of probability: he wouldn't have indulged in his peculiar tone without a reason; it would take a felt predicament or a false position to give him so ironic an accent.

One hadn't been noting "tones" all one's life without recognising when one heard it the voice of the false position.
The dear man in the Paris garden was then admirably and unmistakeably IN one--which was no small point gained; what next accordingly concerned us was the determination of THIS identity.

One could only go by probabilities, but there was the advantage that the most general of the probabilities were virtual certainties.

Possessed of our friend's nationality, to start with, there was a general probability in his narrower localism; which, for that matter, one had really but to keep under the lens for an hour to see it give up its secrets.

He would have issued, our rueful worthy, from the very heart of New England--at the heels of which matter of course a perfect train of secrets tumbled for me into the light.