My friend was standing with an expression of strained intensity upon his face, staring at the railway metals where they curved out of the tunnel. Aldgate is a junction, and there was a network of points. On these his eager, questioning eyes were fixed, and I saw on his keen, alert face that tightening of the lips, that quiver of the nostrils, and concentration of the heavy, tufted brows which I knew so well.

“Points,” he muttered; “the points.”

“What of it? What do you mean?”

“I suppose there are no great number of points on a system such as this?”

“No; they are very few.”

“And a curve, too. Points, and a curve. By Jove! if it were only so.”

“What is it, Mr. Holmes? Have you a clue?”