"That was terrible," murmured Dickie. "Fancy being scared by an old tree," and as they passed he slapped the straggling roots where they came out from the roof.

The passage now ran downhill. It was rough underfoot and the roof was sometimes shored up with planks and supports. In some places the walls were damp.

"We're going downhill fast now," Jon said, "and it's fairly straight... Here's what we smelled burning. Miss B's cigarette-end. It's still alight, so she can't be far ahead. Don't make a row."

The air was fresher now and seemed to be blowing steadily towards them.

"Going uphill again now," Jon said. "Now a turn to the right... Look out, Penny! There are three steps up here... Gosh! I'm out!" and even as he spoke he disappeared. Penny looked up and saw something like branches outlined against a star-spangled sky, and then Jon's hand came down to her and pulled her into the open. When they were all out they realized that they were on a patch of waste ground behind some fishermen's huts standing above the road and the river. The feathery branches of the tamarisks were stirring gently and a great moon sailed serenely over the walls of Rye, which towered up behind them. David's hand came down hard on Penny's shoulder.

"Isn't that what we're looking for?" he said quietly, pointing with the other hand down to the river. Penny wriggled free and stood up. Unmistakable in the clear moonlight, the stumpy figure of Miss Ballinger was crossing the old wooden bridge. In the stillness the sound of her footsteps came faintly to them. Then they heard the whine of a car's self-starter, heard the engine burst into life, heard the gear change and the throbbing gradually die away in the distance.

"So that's how she does it," Penny said. "We've found out a lot tonight, but we haven't found the treasure."

"You see, don't you?" Jon was explaining to anyone who would listen. "You see that the way we've come was the smugglers' secret way up into the town. That's why the Dolphin was marked on the map, and that's why the steps are called 'Trader's Passage'. Smugglers used to be called Freetraders. I bet our secret passage runs under the steps all the way."

"This entrance is well hidden, too," David said. "We must be careful not to leave any signs outside here... Now, I suppose we'd better go back... Which way? Outside or inside?"

"Inside, of course," the twins protested.

They pulled the tamarisk branches over the entrance again and made their way quickly up the passage. When they had all reached the top step safely they remembered that the panel had closed behind David, who had not been able to reopen it.