Captain Andrews was in slightly more familiar territory now as he listened to a top secret briefing from the commanders of the various sections under his authority.

The map that illustrated the bfiefing was created using the very latest upgrade to the LiDAR technology that had superseded the nearly a century old SONAR which the Navy used to depend on. A survey boat had passed back and forwards across the reef continuously for more than forty-eight hours to get such detailed data and it had taken another twenty-four hours to compile it into this detailed schematic of, not only the reef and the sea bed, but what was under the sea bed for more than twenty metres.

This was twenty metres of pre-Cambrian igneous rocks, Ordovician-Devonian Sedimentary rocks, and Triassic-Jurassic volcanic rocks collectively known as the Florida Platform. Essentially, to somebody like Captain Andrews, an intelligent man but one whose expert fields had nothing to do with geology, it was what the State of Florida sat upon.

Most of it was, as anyone might expect, solid rock with just the occasional pocket that might contain pre-Cambrian air, trapped for eons before the once dry land of the Pangean supercontinent broke up.

But one section of the graphic made everyone around the table sit up and stare intently at the wall sized screen.

“Is that…”

“Yes sir,” said the survey leader who fully understood the geology of the Florida Keys but had been as surprised by this revelation as anyone else. “It is a subterranean tunnel, descending from the reef at a gradient of one in four, which is the sort of slope that makes casual cyclists get off and push, but perfectly possible to walk along. The height of the tunnel is two hundred centimetres, or a little over six foot, meaning that an average adult male could stand up comfortably....”

“It’s that height uniformly, all the way down?” asked somebody around the table.

“For as far as our survey went, yes.”

Andrews was not the only one who immediately realised what this meant.

"This isn’t some kind of natural fissure. This tunnel is man-made. It has been put there, right under our noses by… by whom?”

He knew what his own conclusion was. Around the table his colleagues agreed. This had to be enemy agents of some sort. Russians, Koreans, Red Chinese….

“Within throwing distance of our base?” The idea was not just incredible, but frightening. And how had it been done without them knowing?

“It explains the civilian deaths. They must have gotten too close.”

“Our dive team, too.”

“We’ve found no bodies,” Andrews reminded everyone. “There’s still a chance our guys are alive. Now we know where they are. We need to consider how to get them back… before we take any kind of decisive action against… whoever… is down there. Give me a plan of action, please.”

“To rescue our men from a secret underwater lair of enemy agents?” The voice that put the case so succinctly was tinged with dark humour. “Call Stingray. It’s more in their line than ours.”

The laughter was muted by the seriousness of their reality. Andrews repeated his call for a realistic action plan and gave his subordinates an hour to come up with something feasible. Meanwhile he had some thoughts of his own.

“Send a car and get that Doctor and Miss Brown back here,” he ordered. “He knew something about all this. He was paying such close attention to the burn marks on those boats that he didn’t see security closing in on him. And he was trying to warn us off going near the reef. I don’t care what the King or President, or the goddamned Dalai Llama says. I’m going to get the truth out of him.”

“We’re not going to dive?” Peri asked. They had taken the launch to the mainland in the cool evening air and found the TARDIS where The Doctor had parked it behind the boat repair yard at the far end of the marina.

“Short cut,” he answered. “The airlock near the wreck site I saw this morning would take ages to open up. My way is much quicker.”

Despite sometimes missing a destination by thousands of light years and hundreds of years, the TARDIS wasn’t too bad at short distances. They went out to sea in hover mode and descended to the reef. The incongruous blue box made an excellent mini-submarine.

The TARDIS also had its own equivalent of LiDAR. This version was developed for scanning whole planets at once. It didn’t need forty-eight hours to build a composite picture of what was beneath the coral encrusted sea bed. The tunnel big enough for a man to stand upright was easily mapped. The TARDIS was also capable of reading the environment within the tunnel. There was air, slightly less dense than above ground, and with a little less oxygen in proportion to the nitrogen component, but breathable.

“By complete coincidence the wreck was sunk right beside the airlock entrance,” The Doctor noted. “Of course, the bulkhead is very well disguised under sand and coral debris. It wouldn’t be noticed by anyone who didn’t know what Sea Devil technology looked like. I wasn’t completely sure myself at first. It was only when I heard about the deaths at sea that I put two and two together. The Navy have some casualties, as well, though they can’t possibly know what caused their losses.”

“But that means that people have been diving around the entrance for decades,” Peri noted. “The hotel was built and extended over the past ten years making all sorts of noise and disruption. Why has this only been a problem in the past few weeks?”

“That’s a very good question,” The Doctor said. “I should remember to ask. Just let me double check the co-ordinates. We want to materialise in the tunnel, not through the walls or ceiling. That’s always a risk with tight spaces.”

“Double check all you like,” Peri told him. “Don’t let me get in your way.” Materialising through a solid wall of rock didn’t sound healthy. She wanted The Doctor to get this right.

He did, of course. The TARDIS materialised within the tunnel. When Peri stepped out she noticed two things – first the thinness of the air which made her breathe much harder and second, that there was light in the tunnel. It came from recesses in the rock walls but the ‘bulbs’ looked odd and there was no obvious electrical cable.

“The Sea Devils perfected a way to draw electricity from the Earth’s magnetic field,” The Doctor explained. “And a way to distribute it something like the method Nicolai Tesla had in mind to provide free electricity to everyone.”

“That’s what you mean by advanced technology, then? Not weapons, bombs….”

“I’m afraid they have those, too,” The Doctor admitted. “They didn’t choose the Human word ‘devil’ to describe themselves. But that makes them no worse than Captain Andrews and his crew, or even those compatriots of yours who stand by their ‘right to bear arms’.”

The Doctor got quite preachy on that subject as they descended along the tunnel. Peri occasionally offered her point of view, but he hardly seemed to notice. Finally, she halted and made an impassioned plea.

“Look… I can’t walk downhill in this thin air AND argue the merits of gun control. Just… give me a break. Besides, if we’re heading towards these Sea Devils, and they are likely to be armed, shouldn’t we go quietly?”

“There isn’t a lot of point in that, really,” The Doctor answered. “They will be quite capable of scanning us. They probably already know that I’m not from Earth and have a binary cardiovascular system and you’re a Human female.”

“Oh… great… so we’re walking into a trap.”

“Not neccessarily,” The Doctor answered. “They will know that we’re no threat to them – a neutral and unarmed non-terrestrial and a female of the Human kind - the weaker of your two genders.”

“Remind me, when I have the strength to swing my arm, to give you the slap you deserve,” Peri told him. She noted that the tunnel had levelled out at last, and that there was a door ahead. It was the sort of heavy duty door that usually had the word ‘bulkhead’ in front of it. The Doctor examined it carefully.

“Just a door, not a pressurised airlock,” he said. “The one back where we left the TARDIS would be one of those, allowing them to go from air to water safely.”

“They’re amphibian, you said…” Peri remembered. They can do that… like frogs and toads, breathing through their skin when they’re in water.”

“Exactly,” The Doctor said. “Of course, like all amphibians, breathing air is their ‘normal’ state. It is possible to drown a frog if there isn’t enough oxygen in the water around it. The Sea Devils would have the same problem if they were in de-oxygenated water.”

“I… didn’t know that about frogs… or Sea Devils,” Peri admitted. Of course, The Doctor was merely imparting this knowledge while he was working out how to open the bulkhead door. When it gave a slight hiss and swung towards him he gave a triumphant exclamation and dropped the subject altogether.

They stepped from the narrow corridor into a wide cave fitted out with hundreds of glass cases. Inside each one a Human sized figure with reptilian skin stood upright in a sort of suspended animation. Peri noted their slightly glistening blue-green mottled skin, very like a frog, beak-like mouths, large eyes, two possibly vestigial fins on their head and long necks in proportion to their torsos. She noticed webbed hands and feet, both having only three digits each.

“They don’t seem very big,” she noted out loud. “Not much taller or wider than me. I thought they’d be more like… I don’t know… aquatic Genghis Khan hordes.”

“These are juveniles,” The Doctor answered after looking closely. “Teenagers if you like. Still in deep hibernation. There must be adults attending to them. We should find them.”

Peri still wasn’t sure ‘should’ applied to finding the adult Sea Devils, but it was too late now.

The hibernation cave was vast, and the individual chambers in row upon row. Peri wondered just how many there were. The Doctor estimated about five hundred.

All but one very small group – a mere twenty or so – were juveniles.

“Maybe this is a Sea Devil high school?” Peri suggested.

“That is probably not as silly as it sounds,” The Doctor replied. “It is possible that the young were raised in batches. They may have put them into hibernation together. But I would have expected more adults.”

Finally, they reached the far end of the cave. Another bulkhead door blocked the way, though only very temporarily. The Doctor opened it easily and they stepped through.

Another cave lay beyond, though Peri wondered if that was the correct word for something clearly artificial rather than naturally forming. Like the tunnel and the walls of the first cave signs of laser cutting were clear.

But the walls were far from her primary concern. This room was occupied by at least two dozen Sea Devils.

They were all juveniles, some even more juvenile than the others. As the group turned to stare at the intruders one very small one darted behind another which reached out a protective arm. Though there was no obvious way of telling, Peri thought that these two were older and younger sisters.

Some of the males reached for weapons – long spears or harpoons that crackled with electricity. The Doctor held out his arms, palms up, to indicate that he was not armed or a threat to them.

“I come in peace,” he said. “I want to help you, if I can. Where are your Elders?”

“Oh… Doctor…” Peri pointed to a casket made of the same clear material the hibernation chambers were made of. This one rested horizontally and the Sea Devil inside was clearly not sleeping. “Oh… this is a funeral… sort of.”

“Your Elder is dead?” The Doctor asked. The weapons were lowered as he moved slowly and unthreateningly, but they remained in wary hands. Peri approached the two females, her hands open in emulation of The Doctor, and hoping that a friendly smile meant the same in Sea Devil culture.

“Elder Daris was killed by a human,” replied one of the males in a rasping whisper. At the same time The Doctor felt a more powerful telepathic response in his head. The adult called Daris had been instructing the small group of youngsters in spear fishing. It was part of their survival training. Peri’s guess that this was a sort of school had been spot on. For many centuries groups of the young had been revived by one or other of the adults, their teacher, for periods of training, before returning to the hibernation chamber. But in those centuries humans had learnt to make the oceans their territory with scuba diving and snorkelling and it was only a miracle a clash had not happened before now.

The disastrous meeting of the two species had happened just over two weeks ago – or in Sea Devil terms, fifteen diurnal periods. The fishing team had come into contact with a group of Human divers doing much the same thing. Both groups had reacted to each other with shock. Elder Daris had been killed with a hand-held harpoon gun fired by a scared and panicking human. The young Sea Devils had responded by attacking the human divers and their boat, which they burnt from underneath with their electrically powered spears.

“Harpoon fishing around the protected reef is illegal,” Peri said. She had felt the images in her mind, too, and understood what had happened right away. “Those humans were acting illegally. I’m sorry that your teacher was killed by them. That was wrong.”

“Yes, it was,” The Doctor agreed. “But so was the vengeance you have all taken on innocent humans. You’ve behaved in a way quite unbecoming of your proud and civilised race. Your great military commanders would be disappointed by such undisciplined behaviour. Not to mention that you have put your hibernating friends in danger. The humans are not primitive any more. Their military technology could destroy you all.”

The young females shrank away from The Doctor’s words. Peri tried to reassure them gently, but it was clear that they had been living in fear, constantly on the edge of their nerves, ever since they lost the advice and guidance of the Elder.

“We… are sorry,” rasped one of the males who had called himself Grui. He was a sibling to the two females, Ki and Larei. He stood near to them as if trying to protect them both. He and another youth called Briun were trying to assume an Elder position and keep the group together, but they lacked experience and their leadership was shaky.

“I think the best thing you can do is go back into hibernation,” The Doctor said. “If the attacks stop, the humans will lose interest in searching. You will be safe.”

The young Sea Devils responded with despair. They were only children. They didn’t know how to operate the hibernation chambers. That was something the adults did.

“All right, I can sort that out,” The Doctor promised. “You just need to show me the control computer and then get into your chambers.”

“What about our hostages?” asked Ki.

“Hostages?” Peri asked. “What hostages?”

“The humans who stumbled upon our reef airlock. They were taken alive. Briun and Grui both thought… that we might not be attacked in the hive if the humans knew we had some of their men with us.”

“They are safe?” The Doctor asked.

“We have treated them well,” Grui insisted. “They have been given food and drink… and soft, cushioned pallets that they need to sleep upon.”

Briun went to a computer console set in the wall. A screen slid open. The images were of another rock walled room where five men in wetsuits were looking rough after several days without shaving. Their wetsuits had logos on the arms identifying them as belonging to something with the acronym US-SF-UWO.

“United States Army Special Forces Underwater Operations School,” Peri explained. “Based at Key West Naval Air Station. Captain Andrews must know they’re missing. But he wasn’t going to discuss it with civilians like us, even with credentials from the King of Britain.”

“Let me take them back to where they belong,” The Doctor said. “I will make sure there is no retaliation for their capture.”

The young Sea Devils agreed to that plan. The Doctor sent Peri to bring the divers while he followed Briun to the hibernation chamber. The controls were in the ancient language of the Reptilian races, but The Doctor understood it with just a few minutes brushing up on the syntax. The controls were designed for their webbed three fingers, but that wasn’t a huge problem. He managed that easily.

When Peri brought the weary, confused and frightened divers through towards the tunnel where the TARDIS had been left she saw the young Sea Devils taking their places in their chambers. Grui was making sure that Ki and Larei were safely installed. The two females shared a chamber, Larei clinging close to her sister. Grui touched both on their reptilian cheeks before closing the door over them.

“I’m sure they will be all right,” Peri told him. It was strange, knowing that the Sea Devils could kill, and had been thought of as monsters by the humans they encountered, that she wasn’t scared of them. If anything she sympathised with them. She hoped they would be safe from the mighty US military machine that she knew existed.

“Good luck,” she said to Grui as he took the chamber next to his sisters.

“Thank.. you,” he rasped before the door closed. Around him all of the Sea Devils were safe inside their hibernation chambers. Peri saw the cases fill with a light gas of some sort that was part of the hibernation process. Then The Doctor was with her. He herded the group of divers through the chamber and into the tunnel. They asked a lot of questions about the nature of their rescue and their rescuers – an oddly dressed and clearly unarmed man and a young woman in a blouse and shorts. They got no answers.

They had no answers about the TARDIS, either. Peri gave them coffee while The Doctor programmed their return to Key West Naval Air Station. They looked at it with suspicion.

“There isn’t some kind of memory changing stuff in here, is there? To make us forget about sea monsters and English police boxes with space ships inside?”

“No, but that’s not a bad notion,” The Doctor replied. “It would save a lot of trouble in these situations.”

“They weren’t monsters,” Peri said. “You should understand that much, and then leave them alone.”

The divers couldn’t agree about that. They just saw inhuman creatures who had held them captive. Nothing she could say would change that.

Of course, when they arrived at the base everyone was taken into custody. The divers were ushered away for debriefing and medical checks. The Doctor and Peri were brought to the same interrogation room The Doctor had been in before. They waited until Captain Andrews came to speak to them.

“I’ve been in video conference with the King AND the President,” he said tersely. “I can’t have either of you interned for what amounts to treason against the United States even though the men say you collaborated with these sea monsters.”

“They’re NOT monsters,” Peri insisted. “Why can’t you lot see that they’re amazing, intelligent creatures that you could learn so much from?”

“Miss Brown, I was told that the immunity from prosecution extends to any companion HE has, and in your case it WOULD be difficult to proceed. In any case, I suppose I owe you some thanks for releasing the men. But you need to understand that this is none of your concern. Any interference in any actions taken from this Station will not be tolerated.”

“What actions?” The Doctor demanded. “What do you intend to do? What ARE you doing?”

Andrews shook his head. He wasn’t about to discuss the action plan he had agreed with any civilians, let alone this very odd pair.

Besides, he had a feeling neither would be pleased to hear how their actions had helped him decide on the plan. The return of the hostages meant that he didn’t have to send in a rescue team. Plus, the men had been able to give him very valuable information about the underground complex.

The Doctor and Peri were heading back to the TARDIS, accompanied by Andrews and a security detail when they got an inkling of what the Captain’s orders had been. The explosion on the sea bed near the reef was heard as a dull rumble and accompanied by a sudden tidal swell followed by dead fish and other marine life floating to the surface.

“You blew up the entrance to the Sea Devil habitat!” Peri cried out. “You sent down men to blow it up.”

“A SEAL team,” Andrews answered. “With timed explosives. They’re already on their way back.”

“Carnage!” The Doctor lamented. “Blowing up the main airlock would send the sea water rushing into the tunnel at a terrible force. The internal bulkhead will never withstand it. The hibernation chamber will be flooded.”

“Its MURDER!” Peri raged, tears pricking her eyes. “How could you….”

“Any threat to national security….” Andrews began before Peri’s anger drowned him out. “Miss Brown, may I remind you….”

The Doctor was the sensible one this time. He pulled Peri into the TARDIS and slammed the door. It dematerialised right in front of Andrews. He had been warned not only by his own Commander-in-Chief and British royalty, but also by the US-SF-UWS men about The Doctor’s decidedly weird machine, and he had decided he wouldn’t worry about how impossible it was just so long as he and his equally impossible friend were gone.

“Peri, hush,” The Doctor said as he programmed the TARDIS’s flight. “It’s not what you think.”

Peri stopped crying with an effort. She looked up at the video screen. She gave a soft cry. They were in the Sea Devil habitat again, within the hibernation chamber. It was filled with sea water, but the lights were still working. Shy could sea Ki and Larei asleep together and Grui next to them, as well as other faces she had learnt to recognise in the short time she had met them.

“Sea Devil technology is FAR superior to anything humans have developed,” he said. “The lower density of the air inside the habitat means less resistance to the flooding water. There was far less damaging compression. The hibernation systems are undamaged. Pumps will eventually clear the water out of the chambers. The internal doors will seal. When they awake again they will be able to repair the outer airlock. Perhaps by the time those youngsters have completed their education Humans will be ready to share the planet with them.”

“They’d better be,” Peri answered. “Because if they’ re not…. I mean… who are the real monsters?”

“As long as you keep asking that question there is hope for your race,” The Doctor assured her. “Meanwhile, lets go back to the hotel. I expect there will be some excitement about the explosion and its effect on the sealife, but cocktails by the pool won’t be interrupted.”