Doctor Who and the Pescatons ( audio story ) Doctor Who and the Pescatons was the first original , officially licensed audio drama based upon " Doctor Who " . Originally released by Argo Records , the story featured Tom Baker and Elisabeth Sladen , as the Fourth Doctor and Sarah Jane Smith . It was divided into two episodes , complete with opening and closing themes , simulating the televised series . Discounting a couple of radio appearances and an LP version of " Genesis of the Daleks " with added narration , " The Pescatons " was the last time that Baker participated in an original " Doctor Who " audio drama until the " Hornets ' Nest " arc in 2009 . The story was unusual because of its first - person perspective . Though first - person narratives weren ' t entirely without precedent — the earlier " Doctor Who in an Exciting Adventure with the Daleks " had been written from Ian Chesterton ' s point of view — this was the first time that a story had been told from the Doctor ' s perspective , similar to Big Finish Productions ' " Companion Chronicles " series . Until 2010 ' s " Dead Air " , it remained the only original story narrated by the Doctor himself . It was also unusual for its depiction of a genocide devised and led by Sarah and the Doctor , without either character displaying even a tinge of remorse . Publisher ' s summary . The Doctor and his companion Sarah battle against some of the most heinous foes to emerge from the outer universe : The Pescaton s . The Doctor finds himself in the capital city of London , where the population is bewildered and trembling beneath the violent onslaught of a merciless invader . Who or what is the mighty Zor , whose green slanting luminous eyes glare out from the dark of night like giant emeralds ? What is the powerful alien force that is bringing Earth ' s civilisation to a standstill , threatening to annihilate everything in its path ? This is the story of a dying Planet , of a Deadly Weed , and the merciless Creatures themselves . It is a Challenge to the Doctor — a frightening race against time . . . Plot . Part one The TARDIS arrives on a beach by the Thames Estuary at night , and the Doctor and Sarah discover a metallic seaweed there . The Doctor consults with Professor Emerson , who says that three expeditions to recover a recent meteorite from the bottom of the estuary have all vanished . The Doctor goes diving and is nearly killed by something that wraps itself around him , but then lets him go . He discovers that the meteorite is a wrecked spaceship buried under the estuary , and he knows where it comes from The Doctor tells Sarah about the Pescatons , a form of carcharhinidae , or deep water shark . Naturally , the experts scoff until one comes out of the Thames and makes its way to London Zoo in search of salt water . The Doctor confronts it in the Aquarium , where it dies and disintegrates . That night , more meteorites land in the Thames . Part two London is invaded , and the Doctor recalls his visit to planet Pesca , home of the Pescatons . He fell down a chasm into a cavern and met Zor , the leader of the Pescatons who informed him that they were going to use him to find a new home now that their own planet was drying out as it fell towards their sun . Zor used his hypnotic powers on the Doctor , who fought back and escaped . Back in London , Sarah finds an abandoned baby while the military try to shoot the invading Pescatons to no avail . The Doctor distracts a Pescaton by singing Hello Dolly and doing a dance so that Sarah can get away with the child . Finally the Pescatons retreated back into salt water , except for one trapped in an Underground tunnel . The Doctor and Sarah go in search of it , and the Doctor starts playing his piccolo to calm his nerves . The Pescaton retreats at the sound . Professor Emerson helps the Doctor build a high frequency sound trap inside a sewer , and Zor is lured there to be destroyed as the planet Pesca disintegrates in its orbit . Without Zor to control it , the Pescaton invasion ends . Home media releases . This story has been released several times on both cassette and audio CD .