David said promptly, "Miss What's-her-name may have left a clue now which ought to be followed up at once, and if we wait till morning we may miss it. Let's go while the trail is red hot! Much better. Don't you agree, Penny?"

"David is right. Let's get ready at once and explore while the scent is hot. Golly! My heart is banging with excitement!"

"All right then," Jon agreed. "But we do want another torch. This battery is nearly finished. Who's got one?"

"We have," Mary said. "Sorry we forgot it. I'll go down for it."

"I'll come with you," Dickie said. "But let's be quick."

Jon, who wanted to change his dressing-gown for a sweater, went with them. While they were away Penny crouched on the floor by the open panel and David paced up and down behind her.

"I can't hear anything," she whispered, "but it does smell mouldy. I wish the others would buck up. I say, David, I was jolly glad you suggested that we explored this tonight. I couldn't have slept a wink not knowing... And there's another thing. I'd love to hear some more about that secret society of yours some time... I've always wanted to belong to one. P'raps we could start one here?"

David laughed. "I'll tell you one day, but there's nothing against us having you in if the other members agree... Here they come."

And then, when Jon was bolting the door from the inside he went on:

"I wonder if we ought to do that? You don't mind me suggesting it, do you, but if we go down the passage and for any reason can't get back the same way, we wouldn't be able to get into the room tomorrow by the ordinary way, would we?"

Jon slipped the bolt back quickly. "Thanks," he said, "that's sensible... Now then, I'll turn the lamp low and then we're ready. Who shall go first?"

"You," said David promptly. "It's your passage, anyway. Penny next to you with a spare torch, then the two nuisances and then me in the rear to keep them in order and with the other torch."

This seemed to be sensible, so Jon opened the panel wide and stepped in. His torch showed a narrow stone stairway - leading down to the right at the back of the fireplace. Penny, immediately behind him, took his left hand and he noticed how cold her fingers were. Then David whispered:

"We're all in now. What about the panel? I'd better leave it open, hadn't I?... Bother it! It's closed itself. I wonder if I stepped on something to make it do that...? I can't find the latch that Mary worked from the outside. I can't see a knob, or a handle or anything, and I'm wondering how we're going to get back again."

Jon said over his shoulder. "We're off! Be careful not to slip. These stairs are narrow and steep."