"I don't think anything's impossible or odd--in London," answered Hetherwick dryly. "If one had only the least idea as to which quarter of the town that car was driven, one might be doing something!"
"Lots of sub-sections in every quarter, and subsections again in each of those," replied Lord Morradale with equal dryness. "Take some time to comb out this town! No! I think we must trust to Matherfield. Nothing else to trust to, in fact."
But Hetherwick suddenly thought of Mapperley. He began to wonder what the clerk was after, what his notion had been. Then he remembered Mapperley's admonition to look out for a message about that time, and excusing himself from Lord Morradale, he jumped on a bus and went along to the Temple. There, in the letter-box, he found a telegram:
"_Meet me Victoria three o'clock. Mapperley._"
Hetherwick set off for Victoria there and then. But it was only a quarter-past two when he got there, and as he had had no lunch, he turned into the restaurant. There, when he was half-way through a chop, Mapperley found him, and slipped into a chair close by before Hetherwick noticed his presence.
"Thought I might find you in here, sir," said Mapperley. They were alone in a quiet corner, but the clerk lowered his voice to a whisper. "Well," he continued, bending across the table, "I've done a bit, anyhow."
Mapperley produced from his breast pocket some papers, and from amongst them selected an envelope--the azure-tinted envelope which he had picked up from the caretaker's supper table at St. Mary's Mansions.
"You recognise this?" he said, with a sly smile. "You know where I got it. This is the envelope which Baseverie took to the caretaker, with the order to enter Madame Listorelle's flat. You knew that I carried it off, from under the man's nose, last night. But you didn't know why. I only laughed when you asked me."
"This reason," replied Mapperley. "We both noticed that the sheet of paper on which the order had been written by Madame had been shortened--there was no doubt that a printed or embossed address had been trimmed off, rather roughly, too. We noticed that, I say, both of us. But I don't think you noticed something far more important--far, far more important--for our purposes."