Meanwhile in another, kinder, universe...
The Doctor and Romana hurried down the tunnel towards Zaroff's laboratory, the wet dark stone suddenly turning to brightly-lit polished metal. Through the archway, they could hear the scientist addressing his crew. "While the time of final detonation has been brought forward, everything else is to continue according to schedule. No one is to leave their posts. Zero minus five."
"Oh good!" the Doctor announced loudly as they entered. "There's still time before before the firecracker explodes!" He turned to Romana. "You see, I said we weren't going to be late."
Zaroff spared him a glance. "Ah, Doctor. We have been expecting you."
"Doctor," said Romana warningly as they spotted the fish people guards emerging from the shadows on either side of the entrance arch, hissing and burbling angrilly.
"Your sabotage cannot be carried out now," Zaroff said with a lazy smile.
"Sabotage? Us? Nonsense!" replied the Doctor pleasantly. "How could anyone go and sabotage your plan! Imagine all the things that might go wrong!"
"Atlantis and everything in it getting blown to pieces for example," Romana agreed.
"I say, I do hope you've shared your big secret with everyone here," the Doctor added, well aware of the fish people circling them, preparing to strike. "I know everyone down here's devoted to you, but that doesn't mean you can destroy this entire planet without telling anyone."
"What's he talking about, Professor?" asked a confused technician.
"Ah, you see? The public won't stand for it."
"The professor here intends to drain the Atlantic ocean into the fissure you've been drilling," Romana explained, ducking a webbed claw from one of the guards. "All that cold water pouring onto a white-hot molten core."
"An expanding cloud of steam bigger than a billion kettles," agreed the Doctor, bending forward and allowing two of the charging fish people to crash into each other. "Superheated steam with no way to escape and the pressure..."
"...builds up and up and up until the crack we have created splinters the Earth like an egg," completed Zaroff with a delighted smile. "The world will quite possibly fragment, blown apart from the pressure. But either way, all life on the surface shall perish!"
The Doctor's face twisted in confusion. "You mean you know what's going to happen?"
"Of course!" Zaroff laughed. "I promised to lift Atlantis from the sea - I'll go one further and lift it to the sky!"
"In tiny pieces!" Romana protested.
Zaroff nodded, laughing. "It will be magnificent!"
"But why?" wailed one of the technicians.
"Why?" Zaroff spat. "Why not? Science is knowledge and knowledge is power - and you cannot become more powerful than being able to blow up the entire world! There is no greater achievement!"
"How about flooding Atlantis all over again?" suggested Romana coolly.
The Doctor smacked his forehead. "I knew I was forgetting something! Yes, I should have mentioned it earlier - the sea's broken through and in any minute it'll rush in here and we'll all drown." He beamed at them. "I just thought you all should know."
The technicians and even the fish people were looking worried.
"Lies!" Zaroff mocked. "Don't listen to them!"
"Then listen to that roaring in the distance!" Romana challenged."Are you going to tell us the goddess Amdo has indigestion?"
"He's right!" shouted one of the technicians. "Come on!"
The Doctor had to stand to one side as the laboratory staff fled through the tunnel and out of sight. A strong salty breeze was blowing through the archway as the rumbling grew louder. Zaroff shook his head, clearly annoyed but not particularly concerned. "Cowards and traitors," he tutted. "But my creatures have no fear of drowning."
The fish people hissed and gibbered.
"But they have a fear of being blown up," Romana reminded him.
The crested heads and unblinking eyes were turning on Zaroff. "They will obey me," he said confidently.
"Will they?" asked the Doctor.
The creatures began to advance on Zaroff, who just sighed. "It doesn't matter."
He stretched out an arm and flipped a control built into the wall, rather like a light switch. Instantly metal bars shot out from concealed panels in the walls, floor and ceiling, forming a grid that completely sealed off the upper level of the laboratory, isolating Zaroff from the others. "I have anticipated every eventuality, Doctor," Zaroff replied, crossing to the master controls. "You cannot beat me."
"Zaroff!" the Doctor yelled, raising his voice over the roar of the approaching sea. "Time's running out - hadn't you better call it a day?"
"This is my last and greatest experiment! No caution and cowardice like those spineless fools up on the surface! I have conquered and harnessed the powers of nature itself!" Zaroff shouted back. "Nothing can stop me now!"
Romana nudged the Doctor. The floor of the laboratory was wet as sea water began to flow up the steps. "Oh, all right," he sighed wearily. "I tried my best. Come on, Romana."
Zaroff looked up sharply as they headed for the exit. "Where are you going?"
"Bye, bye, Zaroff," the Doctor called over his shoulder.
"You're going to die anyway - so why not stay here and witness the ultimate triumph of man over nature!"
The Doctor waved, and he and Romana left. Water was now lapping at ankle-height as the fish people trilled and gurgled suspiciously. "Come back here!" Zaroff roared. "I hold absolute authority over the entire world! I can cancel out all those meaningless aeons of existence at the push of a button! I can destroy in six seconds for what God labored over for as many days! I ORDER YOU TO COME BACK HERE AND STAND WITNESS TO MY TRIUMPH! ZAROFF ORDERS YOU!"
Zaroff's pathetic rants echoed up the tunnel after them as they climbed the stairs. Water was gushing past their legs, threatening to haul them back down to the laboratory. "Doctor!" Romana called after him. "You know it's actually impossible to destroy the Earth the way he said he would?"
"Of course," the Doctor replied, helping her over a collapsed statue. "All the oceans into that one tiny hole? It would be a leaking tap onto a hot plate, bubbling straight up through the hole. Zaroff might have created the biggest whistle on Earth, but not destroyed it."
"We could have just let Zaroff go ahead with it all along," Romana complained. "The worst he could have done was blown himself up?"
"I doubt he would have accepted defeat graciously, do you?" the Doctor replied. "Besides - us? Not interfere? Where would be the fun in that?"
Behind them, the stairwell suddenly filled with water and Zaroff was finally silenced.
"Oh well, at least his octopus will have something to eat," the Doctor observed. "Come on, let's see how K9's doing..."
Same time next year mofos!