"Might as well have a look round to see what that chap was after," Peter said. "Why the banging? Is he looking for a hollow wall, do you suppose? Dash it, I rejected hidden treasure as altogether too far-fetched, but it begins to look remarkably like it!"
"Personally I don't think we shall find anything," Charles answered. "Still, we can try. What a maze the place is!"
Together they explored all the cellars, but Charles was right, and there was nothing to be seen. Deciding that their nocturnal visitor would hardly attempt another entrance now that his way of ingress had been discovered, they made their way up the stairs again.
As they crossed the hall towards the library door a glimmer of light shone on the landing above, and Margaret's voice called softly: "Peter."
"Hullo!" Peter responded.
"Thank goodness!" breathed his sister, and came cautiously down to join him. In the lamplight her face looked rather pale, and her eyes very big and scared. "That awful groan woke me," she said. "I heard it twice, and called to you, Peter. Then when you didn't answer I went into your room and saw the bed hadn't been slept in. I got the most horrible fright."
"Don't make a row. Come into the library," Peter commanded. "You didn't wake Celia, did you?"
"No, I guessed you and Charles had staged something. Did you hear the groan? What have you been doing?"
"We not only heard it, but on two occasions we caused it," Peter said, and proceeded to tell her briefly all that had happened.
She listened in wondering silence, but when he spoke of the part he believed Strange to be playing, she broke in with an emphatic and somewhat indignant headshake. "I'm sure he isn't a crook! And I'm perfectly certain he'd never make awful noises to frighten us, or put skeletons where we should find them. Besides, why should he?"