"In other words," Wright butted in, "when the victim is thus wired to an iron chair concreted into the floor, even if rescuers arrive they can't take him away with them — not even complete with chair — until they've got a pair of pliers and untwisted the lot... Thank you, Mason. You've done well."

"All this is very ingenious, Gerry," the woman said dubiously. "But in aid of exactly what?"

"It all ties in with the little device we took off Slate," her husband replied. "And with my not unusable talent for mimicry. You were cross about the girl escaping; this will not only bring her back: it will effectively dispose both of her and of her partner — and by her own hand, too." He laughed pleasantly. "Another Martini, my dear?"

The hairs on the nape of April's neck were pricking. What devilry could this mean? How was she to be brought back to the thatched house on the moors and made to kill both herself and the helpless Mark Slate?

"When the big mast goes," the man was saying over the noise of ice in glasses, "it should fall — if our little Satrap in the station has done its homework — diagonally across the control bunker and put the whole place out of action for weeks!"

"And the charge in the chamber where Slate is...?"

"Lies directly under that mast. It's all very neat. As soon as I have called her, I shall set the hour glass in the chamber. The charge will go up when she opens the door — or when the sand has run out of the glass — whichever happens first. By which time, we shall be on the high seas with our final batch of photos, nice and safe and out of harm's way!"

In the cave below the cliffs, April Dancer shivered as she heard this plot unfold. But the maddening thing was — although she had managed to eavesdrop on the whole plan, it still meant little to her; she couldn't act.

"Now, I'll show you exactly what I mean..." Sir Gerald was saying, when suddenly the girl totally lost interest in what it was that he was about to demonstrate.

The Communicator in her handbag was bleeping!

Feverishly, she groped for the pen-shaped device and thumbed the switch. "Channel open," she called huskily.

"April, sweetie — they got me!" Mark Slate's voice came strongly from the instrument. "Look, I've got to talk fast. I may have to pull out at any moment if someone comes... I'm held prisoner in an old smuggler's hide-out — an underground cave in the rock below the radar station. Here's how you find the entrance..."

The girl listened dully. Something was wrong. Something was very wrong indeed.

And then suddenly she had it: the voice! It was coming at her twice: she could hear Slate's voice not only from the Communicator but also through the transistorized receiver in her ear...

In other words, it wasn't Mark's voice at all, but Wright's! This was the "talent for mimicry" of which he had spoken... and it was a talent, too! She might easily have been fooled if she hadn't known of the deception.

The voice completed the directions and broke off. "Quick! I must go off the air now," it said. "Did you get that? Can you make it? Where are you — in the caravan?"

"Yes... yes, in the caravan," the girl replied mechanically, her mind racing. "Hold on, Mark: I'll be there. I'll be there as soon as I can…"

The Communicator went dead, but Wright's chuckle continued in her ear. "Right, my dear," he said. "I'm off to the chamber with the hour-glass."

April looked up to meet the astonished gaze of Ernie Bosustow. "It's all right, Ernie," she said. "I haven't gone mad and started talking to myself! This little thing is a two way radio. Mr. Slate and I use them for talking to one another when we are apart. Wright has just tried to decoy me into coming to the house by pretending to be Mr. Slate."

"They have captured him, then?"

"Yes, I'm afraid they have. From what I've just heard — I left a bug in their living room, and I can hear what it transmits on this little ear plug, see? — From what I've just heard, it seems that Wright and his wife have been spying on the secret station at Trewinnock Tor, taking photographs from their house, collecting secret information from accomplices inside, and picking up gossip from everyone they meet at all the military messes they visit."

"Cor! "Ernie said. "Who for — the Russians?"

"No, Ernie, not the Russians. An organisation much more effective than the secret service of Russia, America or even China; an organisation called THRUSH."

"THRUSH? I never heard of it."

"You wouldn't have. But it's there nonetheless. A world wide syndicate of evil men with unlimited money; a collection of rogue scientists, bankers, industrialists and politicians whose aim is to rule the world. The secrets of Trewinnock Tor are small beer to them — but it all adds up... They have been receiving all the information that Wright collected on micro film — either direct negatives or photographed documents and so on. And the film was collected by couriers who called at Sheila's booth in the circus. When they asked for a certain thing —"

"What thing? What did they ask for?"

"A black Porphyry pixie, as a matter of fact."

"A black Porphyry pixie! So that's why you asked... but, like I said, there are none. You couldn't make 'em."

"Exactly. That was to prevent the film being given to some chance customer by mistake. Sheila didn't know who the couriers were, you see, and nobody is going to ask for a souvenir that doesn't exist by coincidence, are they?... Anyone who did enquire about a pixie in Porphyry had to be the courier. And then they were given a lighthouse in Porphyry — with a secret compartment in which the film was concealed."

"Now it's lighthouses!" he cried, astonished. "Who made 'em, then? I didn't."

"I know you didn't. I think we'll find one of Wright's henchmen worked in stone; there's probably a wheel some where in the house or the outbuildings."

"Did... did Sheila know... about the films, I mean? She was in on it?"

"I'm afraid she must have been," April said gently.

The boy kicked savagely at the sand. "It was him!" he cried. "He talked her in to it! It's his fault!"

"Well, let's get on and get at him. Does that map..." She paused.

"What is it?" Bosustow asked.

"I thought I heard voices — a long way away, but quite clear. Could I have done?"

"Not here, not in this cave. 'Tis too far. Only place you could have heard voices from would have been the Keg-'ole itself — and I didn't notice too many sunbathers in there tonight!"

"Oh, well... never mind. I was saying: Wright thinks I'm in my caravan. He won't expect me to arrive for sometime. But if we could suddenly appear before they expected us, we could take them by surprise... and we'd have a much better chance of overcoming them. Then we could try and rescue Mr. Slate."

"Where've they got him, then?"

"Apparently he's in a cave –– some kind of storeroom used by the smugglers, I gather — right under the masts of the Tor. And they're... they're going to fix some explosive booby trap that goes off as soon as the door is opened — or when the sand runs out of an hour glass, whichever happens first. So when we rescue Mr. Slate, the idea is, we blow up ourselves, him, and the station

"That must be the old commissary that the freebooters used! There is a way down from the middle of a thicket just behind Wright's stables..."