They walked on the grass edging the avenue. On the wet turf their feet made no sound. When they came in view of the house, they saw it was in darkness. No light shone in any window, and the only sound to be heard was the melancholy patter of the rain drops on the laurel bushes. When they saw the porch looking black before them, they left the grass and stepped gently across the drive, the gravel crunching softly beneath their feet. Robin led the way boldly under the porch and laid a hand on the doorknob. The door opened easily and the next moment the four men were in the hall.

As Robin moved to the wall to find the electric light switch, a torch was silently thrust into his hand.

“Better have this, sir,” whispered Manderton. “I have my finger on the switch now, but we’d best wait to put the light up until we know where they are. Where do we go first?”

“Into the sitting-room,” Robin returned.

Switching the torch on and off only as he required it, he crept silently over the heavy carpet to the door of the room in which that morning he had come upon Mary. Manderton remained at the switch in the hall whilst the other two men followed Robin through the door.

The room was in darkness. It struck chill; for the fire had gone out. The beam of the torch flitting from wall to wall showed the room to be empty.

“I don’t believe there’s a soul in the house,” whispered the Chief to Robin.

“Ve are too laite; I have said it!” muttered the Dutchman.

“There is another room leading out of this,” replied Robin, turning the torch on to the blue curtain covering the door leading into the office. “We’ll have a look in there and then try upstairs. Manderton will give us warning if anybody comes down ...”

So saying he drew the curtain aside and pushed open the door. Instantly a gush of cold air blew the curtain back in his face. Before he could disentangle himself the door slammed to with a crash that shook the house.