By Monday I will have your answer.”

When Wilson had gone, Holmes turned to me. “Well, Watson,” he asked. “What do you make of it?”

“I make nothing of it,” I answered. “It is very strange. What are you going to do?”

“Go hear some music,” replied Holmes. “There is a violin concert at St. James’s Hall this afternoon. Come along. We have time to make a stop on the way.”

We took the underground train to Aldersgate. A short walk, and we were in Coburg Square.

One of the corner houses wore a sign that read “J. B. Wilson.” Holmes stopped in front of the house. He thumped on the sidewalk with his stick. He pounded in two or three more spots. Then he walked up and knocked on the door.

Mr. Wilson’s helper answered. He was a bright, clean looking young man.

“So sorry to bother you,” said Holmes. “But can you tell me how to get to the Strand?”

“Third right, fourth left,” the young man answered. He closed the door.

“That,” said Holmes as we walked away, “is the fourth smartest man in London. I have come across him before. Did you get a look at his knees?”

“What about his knees?” I asked. “What do you know, Holmes? Why did you pound the sidewalk like that?”

“My dear doctor,” said Holmes. “This is no time to talk. This is the time to look. Let’s see what lies behind this quiet block.” We turned the corner.

To my surprise, we found ourselves on a busy street. “Let’s see,” said Holmes. “There’s a cigar store. And there’s the City Bank. And there is a restaurant.