"Shall I try to cut through the panel?" he asked.

"No, no!" cried Monte Irvin. "Waste no time. You have a crowbar there.
Force the door from its hinges. Hurry, man!"

"It doesn't work on hinges!" Gray interrupted excitedly. "It slides to
the right by means of some arrangement concealed under the mat."

"Pass that lantern," directed Burton, glancing over his shoulder to
Gunn.

Setting it beside him, the Sergeant knelt and examined the threshold
of the door.

"A metal plate," he said. "The weight moves a lever, I suppose, which
opens the door if it isn't locked. The lock will be on the left of the
door as it opens to the right. Let's see what we can do."

He stood up, crowbar in hand, and inserted the chisel blade of the
implement between the edge of the door and the doorcase.

"Hold steady!" said the Inspector, standing at his elbow.

The dull metallic sound of hammer blows on steel echoed queerly around
the well of the staircase. Brisley and Gunn, standing very close
together on the bottom step of the stair to the third floor, watched
the police furtively. Irvin and Gray found a common fascination in the
door itself, and Seton, cheroot in mouth, looked from group to group
with quiet interest.