"My little cave!" he cackled. "Look at it well, because it's the last thing you'll ever see. The tunnel was bricked up once, but I opened it up again — and this is what I found. But I've never explored it properly. You might get lost, and then if you were caught by the tide —"
He shook to another burst of maniacal merriment.
"You see, this is one shore of a huge underground lake, and it has its own tides, twice a day. When the tide comes up, it reaches nearly to the low part of the roof over your head. That's why the last few steps are so worn away. The water does that… It's long past low tide now. In less than two hours the tide will be up. Oh, yes, and you'll be here to see it… creeping up… while you're chained here. Till it comes right over your heads… up and up… and up—"
"And up," murmured the Saint.
"And you will be here — both of you." Essenden turned his pale eyes upon the girl. "Both of you. I'd have saved you, Jill, but you're too dangerous. You'll have to stay here, too. And I shall wall up the tunnel again, with my own hands, and no one will ever know."
The girl knelt beside the Saint. With one hand she stroked the damp hair back from his forehead; the other hand crept slowly, infinitely slowly, towards his pocket. But the gun that Essenden held still covered them both, and there was the cunning of madness in his eyes.
"I shall chain you up here, and leave you," he rambled on. "Then I shall go upstairs and send the others home. I shall pay them well, and they will ask no questions… Aaaaah!"
He pounced, suddenly, like a tiger; and the girl let out an involuntary cry. Her hand was in the Saint's pocket, but it had encountered the muzzle instead of the butt of his automatic. Foolishly, she tried to work round to the butt. The gun came out of the Saint's pocket as Essenden tore at her wrist; then it fell onto the rock.
Simon rolled over and snatched at it. Essenden kicked. The gun shot away from under the Saint's fingers, spun clattering over the uneven floor, and plopped into the stream a dozen feet away.
"You must have played football for Borstal," said the Saint appreciatively.