"Where?" Hanaud inquired.
"In the big letter-box of the Post Office at the corner of Trafalgar Square."
Hanaud looked at the girl sharply.
"You had your wits about you, I see," he said.
"What if the envelope gets lost?" said Ricardo.
Hanaud laughed grimly.
"If one envelope is delivered at its address in London to-day, it will be that one," he said. "The news of the crime is published, you see," and he swung round to Joan.
"Did you know that, Miss Carew?"
"No," she answered in an awe-stricken voice.
"Well, then, it is. Let us see what the special investigator has to say about it." And Hanaud, with a deliberation which Mr. Ricardo found quite excruciating, spread out the newspaper on the table in front of him.