“We are now,” he said, “going to the factory of Badcomb and Martin, shell importers and cutters, in the West India Dock Road.  If I don’t find my man there, I shall hand the facts over to the police, and waste no more time over the case.”

“What is your man like?” I asked.

“I am looking for an elderly Japanese, wearing a new hat or, more probably, a cap, and having a bruise on his right cheek or temple.  I am also looking for a cab-yard; but here we are at the works, and as it is now close on the dinner-hour, we will wait and see the hands come out before making any inquiries.”

We walked slowly past the tall, blank-faced building, and were just turning to re-pass it when a steam whistle sounded, a wicket opened in the main gate, and a stream of workmen—­each powdered with white, like a miller—­emerged into the street.  We halted to watch the men as they came out, one by one, through the wicket, and turned to the right or left towards their homes or some adjacent coffee-shop; but none of them answered to the description that my friend had given.

The outcoming stream grew thinner, and at length ceased; the wicket was shut with a bang, and once more Thorndyke’s quest appeared to have failed.

“Is that all of them, I wonder?” he said, with a shade of disappointment in his tone; but even as he spoke the wicket opened again, and a leg protruded.  The leg was followed by a back and a curious globular head, covered with iron-grey hair, and surmounted by a cloth cap, the whole appertaining to a short, very thick-set man, who remained thus, evidently talking to someone inside.

Suddenly he turned his head to look across the street; and immediately I recognized, by the pallid yellow complexion and narrow eye-slits, the physiognomy of a typical Japanese.  The man remained talking for nearly another minute; then, drawing out his other leg, he turned towards us; and now I perceived that the right side of his face, over the prominent cheekbone, was discoloured as though by a severe bruise.

“Ha!” said Thorndyke, turning round sharply as the man approached, “either this is our man or it is an incredible coincidence.”  He walked away at a moderate pace, allowing the Japanese to overtake us slowly, and when the man had at length passed us, he increased his speed somewhat, so as to maintain the distance.

Our friend stepped along briskly, and presently turned up a side street, whither we followed at a respectful distance, Thorndyke holding open his pocket-book, and appearing to engage me in an earnest discussion, but keeping a sharp eye on his quarry.

“There he goes!” said my colleague, as the man suddenly disappeared—­“the house with the green window-sashes.  That will be number thirteen.”

It was; and, having verified the fact, we passed on, and took the next turning that would lead us back to the main road.

Some twenty minutes later, as we were strolling past the door of a coffee-shop, a man came out, and began to fill his pipe with an air of leisurely satisfaction.  His hat and clothes were powdered with white like those of the workmen whom we had seen come out of the factory.  Thorndyke accosted him.