“I’ve no idea. It might be a linen-closet—”
Landis was off down the hall. He opened the last door on the left, shut it again and groaned as he rejoined them. “Another flight of stairs! Opens into the hall above this one, I suppose?”
“Never knew it was there!” said Graham in surprise. “Come to think of it, I believe there is a third door on the left upstairs. We’re billeted up there. It’s probably meant for the servants.”
Landis nodded absently. “Well,” he said, “suppose we go back and interview that doctor.”
“Just a minute,” rapped Bernard. He walked heavily toward the end of the hall and tried the door there. It was locked, and his big fingers found the key on the inside.
“Thought you used this hall a lot!” he growled as he came back. “It’s only a bit after ten and the door’s locked!”
“That’s funny,” said Graham. “It’s never locked until midnight as a rule—later, if we’re all out.”
“Well, it’s locked now.”
“Wait a minute!” Graham paused to think.
“We all came through that door before dinner tonight,” he declared at last, “that is, the six of us. I dropped behind with my wife. And I held the door open for her! I’m sure of that! Look here, I was the last one through that door before dinner—I mean, when we came home—and I’m certain I didn’t lock it after me!”