When he looked towards the bar, after seating himself, the waiter, with his back towards Cleggett's corner, was talking in a low tone to the bartender.

But they had both seen him; Cleggett perceived they both knew him.
"See what the gentleman wants, Pierre," said the bartender in a voice too elaborately casual to hide his surprise at seeing Cleggett.
The waiter turned and came towards him, and Cleggett saw the man's face for the first time.

It was a face that Cleggett never forgot.
Cleggett judged the man to be a Frenchman; he was dark and sallow, with nervous, black eyebrows, and a smirk that came and went quickly.

But the unforgettable feature was a mole that grew on his upper lip, on the right side, near the base of his flaring nostril.

Many moles have hairs in them; Pierre's mole had not merely half a dozen hairs, but a whole crop.