Detective-Sergeant Sowerby reported himself in Inspector Dunbar's room at New Scotland Yard.  
“I have completed my inquiries in Wharf-end Lane,” he said; and pulling out his bulging pocketbook, he consulted it gravely.
 
Inspector Dunbar looked up.
 
“Anything important?” he asked.
 
“We cannot trace the makers of the sanitary fittings, and so forth, but they are all of American pattern. There's nothing in the nature of a trademark to be found from end to end of the place; even the iron sluice-gate at the bottom of the brick tunnel has had the makers' name chipped off, apparently with a cold chisel. So you see they were prepared for all emergencies!”
 
“Evidently,” said Dunbar, resting his chin on the palms of his hands and his elbows upon the table.
 
“The office and warehouse staff of the ginger importing concern are innocent enough, as you know already. Kan-Suh Concessions was conducted merely as a blind, of course, but it enabled the Chinaman, Ho-Pin, to appear in Wharf-end Lane at all times of the day and night without exciting suspicion. He was supposed to be the manager, of course. The presence of the wharf is sufficient to explain how they managed to build the place without exciting suspicion. They probably had all the material landed there labeled as preserved ginger, and they would take it down below at night, long after the office and warehouse staff of Concessions had gone home. The workmen probably came and went by way of the river, also, commencing work after nightfall and going away before business commenced in the morning.”
 
“It beats me,” said Dunbar, reflectively, “how masons, plumbers, decorators, and all the other artisans necessary for a job of that description, could have been kept quiet.”
 
“Foreigners!” said Sowerby triumphantly. “I'll undertake to say there wasn't an Englishman on the job. The whole of the gang was probably imported from abroad somewhere, boarded and lodged during the day-time in the neighborhood of Limehouse, and watched by Mr. Ho-Pin or somebody else until the job was finished; then shipped back home again. It's easily done if money is no object.”
 
“That's right enough,” agreed Dunbar; “I have no doubt you've hit upon the truth. But now that the place has been dismantled, what does it look like? I haven't had time to come down myself, but I intend to do so before it's closed up.”
 
“Well,” said Sowerby, turning over a page of his notebook, “it looks like a series of vaults, and the Rev. Mr. Firmingham, a local vicar whom I got to inspect it this morning, assures me, positively, that it's a crypt.”
 
“A crypt!” exclaimed Dunbar, fixing his eyes upon his subordinate.
 
“A crypt—exactly. A firm dealing in grease occupied the warehouse before Kan-Suh Concessions rented it, and they never seem to have suspected that the place possessed any cellars. The actual owner of the property, Sir James Crozel, an ex-Lord Mayor, who is also ground landlord of the big works on the other side of the lane, had no more idea than the man in the moon that there were any cellars beneath the place. You see the vaults are below the present level of the Thames at high tide; that's why nobody ever suspected their existence. Also, an examination of the bare walls—now stripped—shows that they were pretty well filled up to the top with ancient debris, to within a few years ago, at any rate.”
 
“You mean that our Chinese friends excavated them?”
 
“No doubt about it. They were every bit of twenty feet below the present street level, and, being right on the bank of the Thames, nobody would have thought of looking for them unless he knew they were there.”
 
“What do you mean exactly, Sowerby?” said Dunbar, taking out his fountain-pen and tapping his teeth with it.
 
“I mean,” said Sowerby, “that someone connected with the gang must have located the site of these vaults from some very old map or book.”
 
“I think you said that the Reverend Somebody-or-Other avers that they were a crypt?”
 
“He does; and when he pointed out to me the way the pillars were placed, as if to support the nave of a church, I felt disposed to agree with him. The place where the golden dragon used to stand (it isn't really gold, by the way!) would be under the central aisle, as it were; then there's a kind of side aisle on the right and left and a large space at top and bottom. The pillars are stone and of very early Norman pattern, and the last three or four steps leading down to the place appear to belong to the original structure. I tell you it's the crypt of some old forgotten Norman church or monastery chapel.”
 
“Most extraordinary!” muttered Dunbar.
 
“But I suppose it is possible enough. Probably the church was burnt or destroyed in some other way; deposits of river mud would gradually cover up the remaining ruins; then in later times, when the banks of the Thames were properly attended to, the site of the place would be entirely forgotten, of course. Most extraordinary!”
 
“That's the reverend gentleman's view, at any rate,” said Sowerby, “and he's written three books on the subject of early Norman churches! He even goes so far as to say that he has heard—as a sort of legend—of the existence of a very large Carmelite monastery, accommodating over two hundred brothers, which stood somewhere adjoining the Thames within the area now covered by Limehouse Causeway and Pennyfields. There is a little turning not far from the wharf, known locally—it does not appear upon any map—as Prickler's Lane; and my friend, the vicar, tells me that he has held the theory for a long time”—Sowerby referred to his notebook with great solemnity—“that this is a corruption of Pre-aux-Clerce Lane.”
 
“H'm!” said Dunbar; “very ingenious, at any rate. Anything else?”
 
“Nothing much,” said Sowerby, scanning his notes, “that you don't know already. There was some very good stuff in the place............