Purification (audio story)

 was the second story in the audio anthology Purity Unleashed, produced by Big Finish Productions. It was written by Chris Chapman and featured Colin Baker as the Sixth Doctor, Bonnie Langford as Melanie Bush and Imogen Stubbs as Patricia McBride.

Publisher's summary
The Doctor and Mel follow the trail to a port in New Zealand, 1910. A ship is being prepared for a journey to Antarctica and the Doctor realises that this is Captain Scott's Terra Nova expedition. But this is merely the beginning of an intricate scheme to rewrite the future of humanity.

Part one
The Doctor and Mel detect a chronomatic time signature of the person responsible Hebe's disappearance in Lyttelton, New Zealand in 1910 and, upon realising that they have arrived on the day that Terra Nova leaves for Antarctica, the Doctor suspects that the person intends to meddle with Robert Falcon Scott's future. They are forcibly removed from the ship before they can get an audience with Scott and learn that deckhand Thomas Rodden has suddenly and inexplicably decided not to go on the voyage.

Having paid Thomas £200 to disembark Terra Nova, Patricia travels forwards in time to 1911, by which time he has become a chauffeur, and sets up a meeting between him and Martha Curtis, a woman whom he would otherwise never have met. Patricia then heads off to make further changes to the timeline.

The Doctor traces the signature and uses the Time-Space Visualiser (which has no record of Hebe) to view Thomas's life, seeing how he was supposed to board Terra Nova and die after falling overboard onto the ice. He and Mel travel to Hull in 1916 and detect Time Vortex debris which leads them to Patricia, who has come to save Thomas, Martha and their daughter Lizzie's deaths in a bombing and denies being responsible for Hebe's disappearance. After saving the Roddens, Patricia heads to Cambridge 1929 and the Doctor and Mel go after her.

Part two
At King's College, Cambridge, the Doctor and Mel see the eighteen-year-old Lizzie's outline shaking due to her paradoxical nature and learn that Patricia gave her the confidence to do well in her entry interview. They follow Patricia to the Palace of Westminster in 1935 where Parliament, which counts Lizzie as one of its members, votes in favour of funding Jasper Woodward's research into antenatal treatment and then to a rally of the Better Party at which Lizzie is the key speaker. There, Mel keeps Lizzie busy so that Patricia cannot introduce Jasper to her and the Doctor confronts Patricia directly.

Patricia explains that Lizzie and Jasper will together improve the next generation of humanity and lead to longer lifespans, but the Doctor is disgusted and sees it as a show of hatred for the disabled and she threatens him with her time-suit's energy discharge valve. The panicking crowds disperse and, after Patricia kills a police officer who tries to arrest her, the Doctor introduces Lizzie and Jasper and tells them never to speak again for the sake of the universe. Patricia proceeds to kill Jasper and escape into the Time Vortex, but the Doctor uses a vortex tether to capture her until, renaming herself Purity, she gets free and sends the TARDIS out of control.

Cast

 * The Doctor - Colin Baker
 * Mel - Bonnie Langford
 * Patricia McBride - Imogen Stubbs
 * Elizabeth / Martha - Leah Brotherhead
 * Thomas Rodden - Jonny Weldon
 * Jasper Woodward / Sir Gerald / Toby / The Harbour Master - Greig Johnson

Crew

 * Cover Art - Claudia Gironi
 * Director - Helen Goldwyn
 * Executive Producers - Nicholas Briggs and Jason Haigh-Ellery
 * Music and Sound Design - Howard Carter
 * Producer - Jacqueline Rayner
 * Script Editor - Robert Valentine
 * Writer - Chris Chapman
 * Senior Producer - John Ainsworth

Worldbuilding

 * Thomas Rodden is a deckhand from London.
 * Patricia's suit has a perception filter.
 * Thomas becomes a chauffeur in Newcastle.
 * The Doctor uses the Time-Space Visualiser.
 * Mel is behind on Corrie.
 * Norman Humphries is a Member of Parliament.
 * Mel has seen Jasper Woodward on Tomorrow's World.
 * Mel likens the Doctor's hair to Harpo Marx's.
 * The Doctor mentions Elise and Stephen Hawking.
 * The Doctor plants a tracker chip on Patricia.

Continuity

 * Hebe has disappeared thanks to changes to history. (AUDIO: Chronomancer)