Earthfall (audio story)

 was the second story in the audio anthology, Extinction, produced by Big Finish Productions. It was written by Andrew Smith and featured Jemma Redgrave as Kate Stewart, Ingrid Oliver as Petronella Osgood, James Joyce as Josh Carter, Tracy Wiles as Jacqui McGee and introduced Warren Brown as Sam Bishop.

Publisher's summary
Lieutenant Sam Bishop is finishing an assignment in Bangkok when he receives a call from Kate Stewart. She has a new job for him — hunt for a stray Nestene energy unit that has come down somewhere in the Gobi desert.

In Mongolia, Sam is joined by Osgood and they set off into the Gobi. But there are Autons in this desert. They are also looking for the energy unit, and they're ready to kill anyone who comes into contact with it.

Back in London, Kate is becoming suspicious of Simon Devlin's company, and decides to pay him a visit.

Plot
In Bangkok, Sam finds a woman who has been infected and mutated by an alien crystal and uses a stun net to capture her after she becomes hostile. After ordering UNIT to lock the crystal away and transport the woman to Group 6 in Tokyo, he receives a call from Kate telling him to travel to Mongolia to recover a Nestene energy unit which fell to the Gobi Desert after hitting a satellite. Instead of sending Osgood to Africa to assist the tracking teams there, Kate sends her to join Sam.

The Nestene Consciousness is concerned about the lost energy unit and tells Devlin that, if UNIT reach it first, their plans must be accelerated. Devlin, however, has already made arrangements for its recovery.

Osgood and Sam head to Dalanzadgad and are debriefed by Kate using a hologram projector. Josh informs Kate that a discreetly-purchased subsidiary of Devlin Futuretech has increased its purchase of crude oil by over 500% in the last year and it seems likely that Devlin is working with the Nestenes. Kate visits him and asks about his disappearance last year, learning that he suffered from fibrous dysplasia and has had his skull replaced with a plastic one. He reveals that he knows about UNIT and warns her not to interfere with his business given his connections.

Osgood and Sam find the crater, but the energy unit is missing and, after knocking Sam out, Jenna Gold kidnaps Osgood. Sam is found by Tarkhan and taken to his camp where his tribe have the energy unit.

to be completed

Cast

 * Kate Stewart - Jemma Redgrave
 * Osgood - Ingrid Oliver
 * Lieutenant Sam Bishop - Warren Brown
 * Captain Josh Carter - James Joyce
 * Tarkhan - Ramon Tikaram
 * Simon Devlin - Steve John Shepherd
 * Jenna Gold - Karina Fernandez
 * Jacqui McGee - Tracy Wiles
 * The Nestene Consciousness - Nicholas Briggs

Continuity

 * Sam is aware of the Nestene's relationship with UNIT. (TV: Spearhead from Space, Terror of the Autons)
 * Kate gets nervous when sitting in a plastic chair. (TV: Terror of the Autons)