Nayland Smith waved to me to take a stand on the other side of the opened door—­behind it, in fact, where I should be concealed from the view of any one descending the stair.

I stood up and crossed the floor to my new post.

A dull thud told of the trap fully raised and resting upon some supporting joist.  A faint rustling (of discarded garments, I told myself) spoke to my newly awakened, acute perceptions, of the visitor preparing to lower himself to the landing.  Followed a groan of woodwork submitted to sudden strain—­and the unmistakable pad of bare feet upon the linoleum of the top corridor.

I knew now that one of Dr. Fu-Manchu’s uncanny servants had gained the roof of the house by some means, had broken through the skylight and had descended by means of the trap beneath on to the landing.

In such a tensed-up state as I cannot describe, nor, at this hour mentally reconstruct, I waited for the creaking of the stairs which should tell of the creature’s descent.

I was disappointed.  Removed scarce a yard from me as he was, I could hear Nayland Smith’s soft, staccato breathing; but my eyes were all for the darkened hallway, for the smudgy outline of the stair-rail with the faint patterning in the background which, alone, indicated the wall.

It was amid an utter silence, unheralded by even so slight a sound as those which I had acquired the power of detecting—­that I saw the continuity of the smudgy line of stair-rail to be interrupted.

A dark patch showed upon it, just within my line of sight, invisible to Smith on the other side of the doorway, and some ten or twelve stairs up.

No sound reached me, but the dark patch vanished and reappeared three feet lower down.

Still I knew that this phantom approach must be unknown to my companion—­and I knew that it was impossible for me to advise him of it unseen by the dreaded visitor.

A third time the dark patch—­the hand of one who, ghostly, silent, was creeping down into the hallway—­vanished and reappeared on a level with my eyes.  Then a vague shape became visible; no more than a blur upon the dim design of the wall-paper . . . and Nayland Smith got his first sight of the stranger.

The clock on the mantelpiece boomed out the half-hour.

At that, such was my state (I blush to relate it) I uttered a faint cry!

It ended all secrecy—­that hysterical weakness of mine.  It might have frustrated our hopes; that it did not do so was in no measure due to me.  But in a sort of passionate whirl, the ensuing events moved swiftly.

Smith hesitated not one instant.  With a panther-like leap he hurled himself into the hall.

“The lights, Petrie!” he cried—­“the lights!  The switch is near the street-door!”

I clenched my fists in a swift effort to regain control of my treacherous nerves, and, bounding past Smith, and past the foot of the stair, I reached out my hand to the switch, the situation of which, fortunately, I knew.