Unlike the Big Finish CDs, this audio was released on vinyl, in 1976, which makes it better, allowing true audiophiles to experience the full timber of the voices of Tom Baker as the Doctor, Elisabeth Sladen as Sarah Jane Smith, Bill Mitchell as alien bad guy Zor, and three stock recordings of screaming women as the entire population of London.
All of the scenes that aren't dialog between the Doctor and Sarah Jane or the Doctor and Zor are narrated by the Doctor, much like later Doctor Who stories such as Dead Air, the VHS reconstruction version of Shada, or Little Britain.
The Fourth Doctor and Sarah Jane accidentally land in present-day England. They discover some scientists are leading an expedition into the Thames to discover what happened to the last expedition sent into the Thames to discover what had happened to the previous expedition sent into the Thames to discover what had happened to the first expedition that was looking for a meteorite or something. The scientists recognize that the Doctor is a scientific genius, so they let him go instead.
The Doctor finds the meteorite, but it's actually a metal cylinder. Then he's attacked by a creature that's just like seaweed, except also like an octopus, and also metallic, from which he immediately deduces that it's an alien creature descended from sharks. He escapes and returns to the scientists, who tell him that's a stupid idea and he's stupid. So he gives up.
Then the creature comes out of the river, knocks on ladies' doors pretending to be the Fuller Brush man, and kills them. (If you don't get that joke, you don't remember 1976. Hint: Chevy Chase. What do you mean who's Chevy Chase? You young people today, I swear. Google it.) After it kills all of London, it remembers that it's a shark and can't breathe in the air, or in fresh water, so it decides to go to the London Zoo to break into the aquarium, but it dies before it makes it. Scientists, the military, and reporters all come around to poke it with a stick, and it disintegrates.
The end? Nope, a bunch more meteorites drop into the Thames. Cliffhanger!
Meteorites fell all over the world, in every body of salt water. And the Thames, which isn't salt water, as was just established on side one.
The Doctor then narrates the fact that he's going to have a flashback, then narrates the flashback. The short version is he's a dick and the whole thing is his fault. Their planet was dying, they needed a new one, and the Doctor refused to use his mighty knowledge of the galactic universe and solar system to offer them an empty ocean world, so they desperately picked a planet at random, which happened to be Earth. So they're evil.
Everyone in the world knows the meteorites are an invasion, and the aliens are called Pescatons, and everyone decides not to do anything about it except to stay home from work. That night, the Pescatons suddenly attack London, while the streets are empty, and also full of people at work and kids in schools. Nothing can stop them, but then they remember that they're sea creatures and go back to the water, but this time the Thames is fine. It's not clear what the aliens in the rest of the world are doing, but who cares?
The Doctor and Sarah Jane, after finding a stray baby and then ditching it somewhere off-screen, wish that humans had been smart enough to stop wasting time on useless science and instead come up with some kick-ass weapons to kill aliens. Sadly, Mr. Saxon is still decades in the future. Fortunately, they accidentally discover that high-pitched noises can kill the Pescatons, just like in Victor Pemberton's Fury from the Deep.
That's all the information the Doctor needs to commit genocide, so that's what he does. And gloats about it to their dying leader. Fuck aliens!
The great thing about audios is that, not limited by the BBC's effects budget, the writer can imagine anything he wants. And Victor Pemberton imagines everything. All at once. The LP cover shows what looks like a plastic landshark-bear-turtle toy, but the way the aliens are described in the audio is far more glorious.
Being descended from sharks, of course they look like seaweed. And, tentacled, like an octopus, both of its feet huge and webbed. With transparent bodies that are also metallic. And pulsating like jellyfish. Their green glowing eyes illuminate the razor-sharp teeth in their squid-like mouths. And their leader, Zor, looks completely different, covered in metal scales, with an oversized oval-shaped head, with transparent eyes so you can see into his giant computer-like brain.
- Four speaks baby, just like Eleven, but the one they meet won't talk to him.
- Four plays a piccolo whenever he's nervous. He does it all the time. This is an important plot point. If you didn't notice it on TV, it's because you weren't paying attention, not because Victor Pemberton just pulled it out of his ass for this story.
- Sarah Jane talks about how nice it is to finally be back in England, even though this story is supposed to immediately follow The Seeds of Doom.
In many ways, this is like an RTD story three decades ahead of its time. An alien invasion that completely fucks up modern-day London. They're invading because their home planet is dying, but they're still the bad guys. And London was the last place they should have invaded, given the whole oceans thing.
The Doctor is also completely out of character, the plot is stupid, and every line completely contradicts every other line. It's also unabashedly childish and cheap.
But somehow, it's fun anyway. Maybe just nostalgia; if you didn't hear this as a kid in the 70s, maybe you'll hate it. If so, that's understandable, but you still suck.