The Children of Seth (audio story)

 was the third story in the third series of The Lost Stories, produced by Big Finish Productions. It was adapted by Marc Platt, from the original script by Christopher Bailey, and featured Peter Davison as the Fifth Doctor, Sarah Sutton as Nyssa and Janet Fielding as Tegan Jovanka.

Publisher's summary
During one of Nyssa's experiments, the TARDIS' temporal scanner picks up a message: "Idra". Just one word, but enough to draw the Doctor to the Archipelago of Sirius.

There, the Autarch is about to announce a new crusade. A mighty war against Seth, Prince of the Dark...

But who is Seth? What is the secret of Queen Anahita, Mistress of the Poisons? And what terror awaits on Level 14?

Part one
Despite being forbidden from visiting her husband without his express permission, the disfigured Queen Anahita sneaks to the Autarch's rooms at night and has her servant, Mira, open his sonic lock. High Minister Byzan finds them and accuses them of attempting an assassination, sending Anahita back to her rooms and having Mira reassigned to Level 14 with her mind wiped after she fails to divulge any information. The next day, on the Autarch's birthday, Byzan prepares a speech declaring war on the planets outside of the rim on the pretence that they are sheltering their enemy, Seth.

Nyssa has devised a program based on probability theory and transmits a question from the TARDIS which is answered by a message from the Archipelago of Sirius saying "Idra". The Doctor attempts to materialise the TARDIS at the message's origin, but the ship is held in a time-space probability lattice and is unable to decide which of the possible futures to travel into. A low-level intelligence drone breaks in and scans the console, designating the Doctor, Nyssa and Tegan as hostile intruders and blowing up whilst attempting to calculate the TARDIS's infinite coordinates. The ship gets through the lattice and materialises in the Imperial City in the Sirian Empire.

The Doctor, Nyssa and Tegan are mistaken for off-world guests and listen to Byzan's speech. Shamur, who calls himself a wanderer between heaven and the world, arrives with weapons and a helmet from the Plains of Ragnarok in search of his granddaughter and says that he has come to speak with the Autarch, but Byzan orders him to leave. He hits Dario Varidi with his stick when he attempts to remove him by force and Nyssa draws attention to herself and the Doctor when she calls Dario an android. Realising that they are the ones who breached the defence net, Byzan gives them the choice of interrogation or a mind wipe.

Part two
Tegan sees the Doctor and Nyssa being arrested and is kept from getting involved by Anahita, who met the Doctor in one of his previous incarnations when she was a student and is the one who sent the message to the TARDIS, "Idra" being her original name. She covers for Tegan by claiming that she is her new servant, gifted to her by the Autarch, and takes her to the Imperial Judiciary to rescue the Doctor and Nyssa, imprisoned with Shamur. Byzan visits the three prisoners disguised as a priest and listens to Shamur's story of the battle on the Plains of Ragnarok being a hallucinogenic-fuelled exercise in which the imperial soldiers killed one another.

Byzan has Albis, his android private secretary, take Nyssa for interrogation, but Albis shows initiative and subjects her to a mind wipe and an assignment to Level 14. Tegan arrives in the dungeon and kisses the guard with a paralysing agent, allowing her to release the Doctor and learn what has happened to Nyssa before heading to Anahita's quarters where they are joined by Shamur, who has had a fruitless audience with the Autarch. A patrol drone like the one that broke into the TARDIS attacks Anahita, but the Doctor has it determine an answer to Nyssa's question and uses the opportunity to plug himself into the defence net. He is overwhelmed with numbers and loses his sight.

Part three
to be added

Part four
to be added

Cast

 * The Doctor - Peter Davison
 * Tegan Jovanka - Janet Fielding
 * Nyssa - Sarah Sutton
 * Queen Anahita - Honor Blackman
 * Byzan - Adrian Lukis
 * Autarch Siris - David Warner
 * Shamur - Vernon Dobtcheff
 * Albis - Matt Addis
 * Mira - Emerald O'Hanrahan
 * Radulf Varidi - John Banks

Continuity

 * The Doctor believes that the TARDIS team's recent visit to Luparis had a therapeutic effect on Nyssa (AUDIO: Hexagora) following her brainwashing at the hands of the Elite on Florana. (AUDIO: The Elite)
 * Tegan does not regret her decision to remain in the TARDIS as opposed to returning to Brisbane, Australia in 1983 with her former boyfriend Mike Bretherton. (AUDIO: Hexagora)
 * The Doctor would become blind again in his twelfth incarnation. (TV: Oxygen)