Dethras (audio story)

 was the fourth story in the sixth series of the Fourth Doctor Adventures, produced by Big Finish Productions. It was written by Adrian Poynton and featured Tom Baker as the Fourth Doctor and Lalla Ward as Romana II.

Publisher's summary
In the control room of a World War 2 submarine something strange has started to happen. As the ship runs out of control, its crew begin to fall unconscious...

Finding the submarine in the last place they'd have expected, the Doctor and Romana are confronted by a mystery. Once fully populated, there are now only three men on board. And there's now also a chimpanzee.

What has happened to the rest of the crew? What are the strange noises they can hear outside the hull?

And most importantly, who, or what, is Dethras?

Part one
Applying the randomizer for the first time in several journeys, the TARDIS lands on a stricken WWII British submarine. On board are three naval soldiers, John, Philip and Robert, along with a chimpanzee called Franklin.

The panicked crew reveal they have no idea how Franklin got on board and the sub is near to collapse, but not because it has sunk to the bottom of the ocean - the submarine is adrift in space, just one more vessel in a vast spaceship graveyard in orbit around a desolate planet!

Meanwhile, on a spaceship elsewhere, Commander Flague is leading a mission to locate something, or someone, called Dethras...

The submarine is attacked by creatures living in the vacuum of space. The creatures gain access to the sub, ripping open the hold where the TARDIS landed, expelling the police box into the void.

When crewman Robert starts to mutate into one of the space creatures, the Doctor amplifies the submarine's comms system, which activates the closest working emergency transmat among the spaceships outside.

The Doctor and John appear on a nearby ship, while Romana, Philip and Franklin are transported to another ship. Franklin has begun to exhibit human speech and his vocal skills are rapidly improving.

Suspecting John is not who he says he is, the Doctor confronts the crewman, who admits that he isn't John at all, but none other than Dethras!

Part two
to be added

Cast

 * The Doctor - Tom Baker
 * Romana - Lalla Ward
 * John - Alistair Petrie
 * Flague - Sheila Ruskin
 * Philip - Josh Bolt
 * Robert - Brian Vernel
 * Franklin - John Banks
 * Xankari / Teacher - Jane Slavin

Continuity

 * The Doctor has been bypassing the randomiser for a few journeys. (AUDIO: The Beast of Kravenos, The Eternal Battle, The Silent Scream)
 * Romana states the Black Guardian is bound to find them again. (PROSE: The Well-Mannered War, AUDIO: Casualties of Time)
 * The Doctor uses his etheric beam locator. (TV: Genesis of the Daleks)
 * Time Lords can survive for a short time in the vacuum of space. (TV: Four to Doomsday)
 * The Sixth Doctor will later encounter Voord that quick-evolve themselves into Cybermen. (COMIC: The World Shapers)
 * The Doctor still wishes to go to Brighton to visit the sea-side. (TV: The Leisure Hive)