"I'll go," Plummer said to me hurriedly. "Plainly somebody's spotted me in the street, and I may as well hear him."
I knew very well, of course, what Moon meant by a 'nark.' A 'nark' is an informer, a spy among criminals who sells the police whatever information he can scrape up. Could it be possible that this man had anything to tell about Mayes? It was scarcely likely, and I made up my mind that Plummer was merely being detained by some tale of a petty local crime.
But in a few minutes he returned with news of import. "This fellow is most valuable," he said. "He knows a lot about Mayes, whom, of course, he calls by another name; but the identity's certain. He saw me looking in at No. 8, he says, and guessed I must be after him. He seems to have wondered at Mayes's mysterious movements for a long time, and so kept his eye on him and made inquiries. It seems that Mayes sometimes uses a back way, through the window you saw on the opposite side of the little area, by way of that ladder you mentioned. It's quite plain this fellow knows something, from the particulars about that ladder. He wants half a sovereign to show me the way through a stable passage behind and point out where our man can be trapped to a certainty. It'll be a cheap ten
