"There's another thing, too," said Win, lying flushed and pleased against his pillows. "I spent a lot of time on that dividing partition wall. I'm sure there is no space in it unless it is so thick that even a hollow place wouldn't sound any different. But after I looked again at the plans, I saw that what I should have put my time on wasn't that wall at all, but the northern one, indicated here as parallel to the dotted line. Mr. Max, I'm quite certain that the old original cellar extends farther to the north than this newer part. I mean that the north wall of the new cellar isn't on a line with the old one, not in reality, though here it is intended to look so."
"You mean," said Max, bringing intelligent brows to bear on this explanation, "that this was an underground passage rather than a surface path and that its northern side is the one flush with the original cellar?"
"That's exactly it," said Win. "I think there is a passage running along outside that northern wall down to the cave and the beach. There seems a space on the plan that isn't accounted for in any other way, and that explains why this dotted line runs inside the foundations."
"But, old chap," said Max kindly, "I know that cave from top to bottom.
Truly there is no exit. I've spent hours in exploring the place."
"But when I was on the ledge at the back, there was a draught of fresh warm air from somewhere," Win pleaded. "And Roger said he noticed it when you took him there. Behind the ledge is a big pile of stones and rubble. Couldn't that air get in somehow?"
"It must, since you felt it," agreed Max sensibly. "If I can possibly manage it, I'll make an investigation. But I am booked to sail on Tuesday morning. It may have to stand over until the Easter holidays. I will take a squint at the cellar though this very evening. Did you sound that north wall?"
"No, I didn't," Win admitted. "I spent all my time on the west one. Not until I studied the plans again, did it fully dawn on me that perhaps that line was a passage instead of a path. If that is true, it is the other wall that will bear investigation."
Max still surveyed the plans, his fine young face intent on this problem. He glanced up to meet a very wistful look from Win.
"On the whole, let's wait until Easter," he suggested. "Then you'll be feeling more fit and can come down in the vaults with me."
"I wish you'd inspect that wall," Win replied. "If you find it does sound hollow, will Colonel Lisle let us punch a hole?"