Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
Kill or Cure (also called Precis) was an audio story plotted by Iain McLaughlin for the fourth series of BBV Productions' Audio Adventures in Time & Space line in 2001/2. The scripts were never written as BBV were scaling back the line.
It would have been the latest in the series of Zygon audio stories.
Katya "Kat" Dylan and her ex-boyfriend Dave McCormick are the presenter and cameraman for a Blue Peter type show, visiting a South American conservation lab. They aren't happy about working with each other. The 'conservation' by Dr Mueller is actually cover for Dr Imogen Peterson's real scientific work, using the Wo Jifu flower to create a miracle drug; guerillas have been targeting it and a large explosion happened last night. Captain Sanchez, in charge of security, is worried Dylan will find out the guerillas exist and make the country look bad. Sanchez spots an unfamiliar soldier and pursues him to Mueller's tent, but Mueller claims he's seen no-one.
The presenter's jeep is shot at by guerillas. Sanchez lies that this is a military conflict in a neighbouring country spilling over the border, and notes McCormick seems to know more about military matters than a children's TV cameraman should. Meanwhile, guerilla leader Marina Silvestra has found the tortured body of one of her men and assumes it's a warning to leave the area.
When Dylan and McCormick film a soldier trying to break into Peterson's hunt, they're arrested - while Silvestra captures the fleeing soldier for interrogation but finds he won't talk. McCormick says he was a war cameraman who'd stopped taking dangerous jobs because Dylan asks, but Sanchez reveals McCormick had killed someone while covering the SAS and given 'special privileges'. Soon, government patrols are being ambushed and Sanchez decides he needs to call for an airlift to get the lab out. Silvestra is listening in and decides to attack the compound when the helicopter arrives. The captured soldier escapes.
Dylan and McCormick escape jail and find Sanchez searching the same hut - when a second Sanchez arrives. They fight and one escapes. Right after, the guerillas attack and shoot down the chopper. While Sanchez is distracted, the reporters and Peterson discover the blood from his wound isn't human. Silvestra discovers the fleeing Sanchez, who transforms into a Zygon before both of them are captured. The real Sanchez, who thinks this discovery will help him in a political career, assumes the guerillas are working with aliens but Silvestra thinks the government is. The reporters are forced to record the Zygon's discovery and make Sanchez look good on pain of 'accidental' death.
When Silvestra sees Dr Mueller, she panics: she's seen his corpse earlier, meaning he's another Zygon. 'Mueller' flees. Now it's clear neither military faction is with the aliens, they team up to hunt him down. Dylan saw the other Zygon was scared of 'Mueller' and questions him. There turn out to be two Zygon factions feuding with each other: both want to conquer Earth and want to kill humanity, but one wishes to slowly terraform planets and the captive Zygon's want to genetically alter their species to better adapt to new worlds (planning to use the drug Peterson's working on).
Silvestra and Sanchez discover a Zygon ship, which explodes. Both seperately return to the compound, wounded and claiming the other is a Zygon in disguise. They release the captive Zygon to see which he attacks - which is Sanchez. The compound then comes under attack by a Zygon craft; the humans realise they can use toxic chemicals in Peterson's work against the enemy. As they run to the hut to get the material, McCormick admits to Dylan he hadn't cheated on her as she thought but had kept seeing their boss in secret to get moved back to news because he knew she would be getting a job offer there. He'd been too angry she'd believed he was having an affair to reveal he wasn't.
The toxic chemicals are able to destroy the Zygons but also the Wo Jifo plants. Peterson decides to remain in the jungle to continue her research in the hope of fame and money; Silvestra will help her to make the rebels look good. McCormick reveals to Dylan that he preserved the camera tape and they have a scoop for the news about aliens. (REF: Downtime – The Lost Years of Doctor Who)