And, taking leave of M. Desmalions and Maître Lepertuis, he went out with
Sergeant Mazeroux.
As soon as they were outside, he told Mazeroux what he knew. The detective seemed much impressed by his companion's professional gifts and quite ready to be guided by his views.
They decided first to go to the Café du Pont-Neuf. Here they learned that Inspector Vérot, who was a regular customer of the place, had written a long letter there that morning. And the waiter remembered that a man at the next table, who had entered the café at almost the same time as the inspector, had also asked for writing-paper and called twice for yellow envelopes.
"That's it," said Mazeroux to Don Luis. "As you suspected, one letter has been substituted for the other."
The description given by the waiter was pretty explicit: a tall man, with a slight stoop, wearing a reddish-brown beard cut into a point, a tortoise-shell eyeglass with a black silk ribbon, and an ebony walking-stick with a handle shaped like a swan's head.
"That's something for the police to go upon," said Mazeroux.
They were leaving the café when Don Luis stopped his companion.
"One moment."
"What's the matter?"
"We've been followed."