The party came to the back door of the house.  Lemerre tried the handle of the door, and to his surprise it yielded.  They crept into the passage.  The last man closed the door noiselessly, locked it, and removed the key.  A panel of light shone upon the wall a few paces ahead.  The door of the lighted room was open.  As Ricardo stepped silently past it, he looked in.  It was a parlour meanly furnished.  Hanaud touched him on the arm and pointed to the table.

Ricardo had seen the objects at which Hanaud pointed often enough without uneasiness; but now, in this silent house of crime, they had the most sinister and appalling aspect.  There was a tiny phial half full of a dark-brown liquid, beside it a little leather case lay open, and across the case, ready for use or waiting to be filled, was a bright morphia needle.  Ricardo felt the cold creep along his spine, and shivered.

“Come,” whispered Hanaud.

They reached the foot of a flight of stairs, and cautiously mounted it.  They came out in a passage which ran along the side of the house from the back to the front.  It was unlighted, but they were now on the level of the street, and a fan-shaped glass window over the front door admitted a pale light.  There was a street lamp near to the door, Ricardo remembered.  For by the light of it Marthe Gobin had seen Celia Harland run so nimbly into this house.

For a moment the men in the passage held their breath.  Some one strode heavily by on the pavement outside—­to Mr. Ricardo’s ear a most companionable sound.  Then a clock upon a church struck the half-hour musically, distantly.  It was half-past eight.  And a second afterwards a tiny bright light shone.  Hanaud was directing the light of a pocket electric torch to the next flight of stairs.

Here the steps were carpeted, and once more the men crept up.  One after another they came out upon the next landing.  It ran, like those below it, along the side of the house from the back to the front, and the doors were all upon their left hand.  From beneath the door nearest to them a yellow line of light streamed out.

They stood in the darkness listening.  But not a sound came from behind the door.  Was this room empty, too?  In each one’s mind was the fear that the birds had flown.  Lemerre carefully took the handle of the door and turned it.  Very slowly and cautiously he opened the door.  A strong light beat out through the widening gap upon his face.  And then, though his feet did not move, his shoulders and his face drew back.  The action was significant enough.  This room, at all events, was not empty.  But of what Lemerre saw in the room his face gave no hint.  He opened the door wider, and now Hanaud saw.  Ricardo, trembling with excitement, watched him.  But again there was no expression of surprise, consternation, or delight.  He stood stolidly and watched.  Then he turned to Ricardo, placed a finger on his lips, and made room.  Ricardo crept