"But, again, supposing it _were_ Laker? Might he not have given his name, and displayed his wallet, and so on, while buying a ticket for France, in order to draw pursuit after himself in that direction while he made off in another, in another name, and disguised? Each supposition was plausible. And, in either case, it might happen that whoever was laying this trail would probably lay it a little farther. Charing Cross was the next point, and there I went. I already had it from Plummer that Laker had not been recognised there. Perhaps the trail had been laid in some other manner. Something left behind with Laker's name on it, perhaps? I at once thought of the umbrella with his monogram, and, making a long shot, asked for it at the lost property office, as you know. The guess was lucky. In the umbrella, as you know, I found that scrap of paper. That, I judged, had fallen in from the hand of the man carrying the umbrella. He had torn the paper in half in order to fling it away, and one piece had fallen into the loosely flapping umbrella. It is a thing that will often happen with an omnibus ticket, as you may have noticed. Also, it was proved that the umbrella _was_ unrolled when found, and rolled immediately after. So here was a piece of paper dropped by the person who had brought the umbrella to Charing Cross and left it. I got the whole advertisement, as you remember, and I studied it. 'Yob' is back-slang for 'boy,' and it is often used in nicknames to denote a young smooth-faced thief. Gunter, the man I suspect, as a matter of fact, is known as the 'Hoxton Yob.' The message, then, was addressed to some one known by such a nickname. Next, 'H.R. shop roast.' Now, in thieves' slang, to 'roast' a thing or a person is to watch it or him. They call any place a shop--notably, a thieves' den. So that this meant that some resort--perhaps the 'Hoxton Row shop'--was watched. 'You 1st then to-night' would be clearer, perhaps, when the rest was understood. I thought a little over the rest, and it struck me that it must be a direction to some other house, since one was warned of as being watched. Besides, there was the number, 197, and 'red bl.,' which would be extremely likely to mean 'red blinds,' by way of clearly distinguishing the house. And then the plan of the thing was plain. You have noticed, probably, that the map of London which accompanies the Post Office Directory is divided, for convenience of reference, into numbered squares?" "Yes. The squares are denoted by letters along the top margin and figures down the side. So that if you consult the directory, and find a place marked as being in D 5, for instance, you find vertical divisions D, and run your finger down it till it intersects horizontal division 5, and there you are."