Gianapolis turned, as Soames stepped up beside him.

“If you will glance back,” he said, “you will see exactly where the door is situated.”

Soames did as directed, and suppressed a cry of surprise.  Four of the stone blocks were fictitious—­were, in verity, a heavy wooden door, faced in some way with real, or imitation granite—­a door communicating with the steps of the catacombs.

“Observe!” said Gianapolis.

He closed the door, which opened outward, and there remained nothing to show the keenest observer—­unless he had resorted to sounding—­that these four blocks differed in any way from their fellows.

“Ingenious, is it not?” said Gianapolis, genially.  “And now, my dear Soames, observe again!”

He rolled back the folding gates; and beyond was a garage, wherein stood the big limousine.

“I keep my car here, Soames, for the sake of—­convenience!  And now, my dear Soames, when you go out this evening, Said will close this entrance after you.  When you return, which, I understand, you must do at ten o’clock, you will enter the garage by the side door yonder, which will not be locked, and you will press the electric button at the back of the petrol cans here—­look! you can see it!—­the inner door will then be opened for you.  Step this way.”

He passed between the car and the wall of the garage, opened the door at the left of the entrance gates, and, Soames following, came out into a narrow lane.  For the first time in many days Soames scented the cleaner air of the upper world, and with it he filled his lungs gratefully.

Behind him was the garage, before him the high wall of a yard, and, on his right, for a considerable distance, extended a similar wall; in the latter case evidently that of a wharf—­for beyond it flowed the Thames.

Proceeding along beside this wall, the two came to the gates of a warehouse.  They passed these, however, and entered a small office.  Crossing the office, they gained the interior of the warehouse, where chests bearing Chinese labels were stacked in great profusion.

“Then this place,” began Soames...

“Is a ginger warehouse, Soames!  There is a very small office staff, but sufficiently large to cope with the limited business done—­in the import and export of ginger!  The firm is known as Kan-Suh Concessions and imports preserved Chinese ginger from its own plantations in that province of the Celestial Empire.  There is a small wharf attached, as you may have noted.  Oh! it is a going concern and perfectly respectable!”

Soames looked about him with wide-opened eyes.

“The ginger staff,” said Gianapolis, “is not yet arrived.  Mr. Ho-Pin is the manager.  The lane, in which the establishment is situated, communicates with Limehouse Causeway, and, being a cul-de-sac, is little frequented.  Only this one firm has premises actually opening into it and I have converted the small corner building at the extremity of the wharf into a garage for my car.  There are no means of communication between the premises of Kan-Suh Concessions and those of the more important enterprise below—­and I, myself, am not officially associated with the ginger trade.  It is a precaution which we all adopt, however, never to enter or leave the garage if anyone is in sight."...