message, to prove it.”
He pulled the waterproof package from his pocket and held it out to Wiggins, who snatched it from him and tried to tuck it out of sight as quickly as possible.
“I think you’d better tell me exactly what’s going on,” Dr Watson said, looking worried. “It sounds as though it could be very dangerous.”
“But, we promised…” Beaver began.
“Whatever your secret is, you can trust me to keep it. I give you my word.”
“That’s good enough for me,” said Sarge. “You can tell him.”
“I may even be able to help you,” the doctor added.
And so, with Beaver chipping in a few extra details, Wiggins quickly explained the situation to Dr Watson, who listened very carefully, then blew out his cheeks with a low whistle.
“My word,” he said. “If this is true…”
“Course it’s true!” Wiggins protested.
“Forgive me. I didn’t mean to doubt you, my dear Wiggins.”
“Good. You’d best come and meet Mr Murray and let him tell you hisself. We gotta give him this letter anyway.”
With Sarge keeping watch, Wiggins led the other three Boys and Dr Watson through the Bazaar to Mrs Pettigrew’s boarded-up shop. He gave three short knocks on the door followed by another two, the signal they had agreed with Mr Murray, who let them in and closed the door quickly behind them.
“I thought you promised not to tell anybody,” Mr Murray admonished when he saw the doctor.
“This ain’t just anybody,” Wiggins replied. “This is Dr Watson. He works with Mr Holmes.”
Murray’s face cleared. “Mr Sherlock Holmes?” he asked. “Then you are welcome, Doctor. I presume the Boys have told you about my situation?”
“They have. It is a great pity Holmes is not here. He would have relished a case like yours. I shall do my best to contact him, but when he is working under cover he is almost impossible to locate.”
“That is as it should be,” said Murray. “In the meantime, it seems the Baker Street Boys have something to report.” He turned to Rosie and Sparrow, who were bouncing up and down with impatience. “Yes?”
“Yes!” Rosie cried. “We found a secret message!”
“What Sir Charles’s henchman hid!” Sparrow added. “Show him, Wiggins.”
Wiggins pulled the letter from his pocket and handed it to Murray, who unwrapped the waterproof cloth and examined the envelope carefully.
“There is no name or address written on it. And it’s firmly sealed. You haven’t tried to open this?” he asked.
Rosie and Sparrow shook their heads.
“Good. We shall need a little steam. Fortunately, I was about to make myself a cup of tea, so we’re halfway there already.” He pointed to a kettle which was heating up on a small spirit stove in a corner of the shop. “As you can see, the good Sergeant Scroggs has provided me with a few home comforts. Now, while we are waiting for the water to boil, tell me how you found this letter.”
Rosie and Sparrow recounted all that had happened, and how they had seen Fredericks chalking a mark on the bridge and then discovered the hiding place.
“Well done!” said Murray. “That’s what is known as a dead-letter drop. A hiding place where a secret agent can leave or pick up messages without risking being seen meeting the other person. The chalk mark would be a sign that there is a message waiting to be collected.”
“That’s devilish clever, and no mistake!” exclaimed Dr Watson. Then he turned to Rosie and Sparrow, puzzled. “But how could you know it was for Moriarty?”
“Because the sign that Fredericks chalked on the bridge was a letter ‘M’,” said Rosie.
“‘M’ for Moriarty!” cried Wiggins. “Of course! Well done.”
“Who or what is Moriarty?” asked Murray.
“Professor Moriarty is an evil genius,” replied Dr Watson. “Holmes calls him the Napoleon of crime. He regards him as his most fearsome opponent.”
“You have encountered him before?” Murray asked Wiggins.
“We’ve