The Poison Sky

Writer:  Helen Raynor           
Director: Douglas MacKinnon

Increase the ATMOS devices to maximum!
Choke them!
Behold the clone world is born!!

The sky is filling with the poisonous Sontaran gas and Wilf is still trapped inside Sylvia’s car. Sylvia appears with an axe, breaks the car windscreen and frees him. 
They take refuge inside their house whilst Donna and The Doctor head back to UNIT HQ.

At UNIT the clone of Martha accesses the computer systems and downloads the NATO security protocols. The Doctor sends Donna into The Tardis and then tells Col Mace that his plan is to use The Tardis to get on board the Sontaran ship. The clone overhears him and arranges for the Sontarans’ to teleport The Tardis away before The Doctor can return to it.

The Doctor and the clone go in search of The Tardis only to discover that it has gone. The Doctor knows that the Sontarans must have had help from somebody on Earth to get The Tardis and because of her lack of concern when The Doctor ask about her family he knows that Martha is not who she claims to be.

At the Rattigan Academy Luke tells the others what they have really been working on, equipment which will allow them to build a brand new Earth on a distant planet. He tells them that he chose them specially because they were the cleverest but they are more concerned about getting back to their families and friends and one by one they run out on him.

UNIT have located the Sontaran ship in orbit above the Earth. The Doctor makes contact with it and taunts General Staal by telling him that poison gas is the weapon of a coward. Staal retaliates by showing The Doctor the captured Tardis and knowing that Donna can now see and hear him he uses coded words and actions to tell her to find Martha’s mobile phone and be ready when he calls.

UNIT are co-ordinating a world wide nuclear strike against the Sontaran ship even though The Doctor has told them that it will have no effect. Col. Mace tells him that with the gas levels nearing critical they have no choice. As the countdown reaches zero the clone uses the NATO codes to stop the launch.

The Sontarans send an attack squad lead by Commander Skorr to the factory to protect the clone and the information she has. They engage a small troop of UNIT soldiers and by exciting the copper in their bullets cause the soldier’s guns to jam.  Col Mace then orders all his troops to engage the Sontarans but without the use of their guns they are quickly overpowered and have to withdraw from the factory. 

On the Sontaran ship Rattigan reports that he has failed to convince his fellow ‘students’ to join him only to discover that there was never going to be a ‘new earth’ and that all the Sontarans had wanted him for was to distribute the ATMOS devices. Rattigan escapes via the teleport just as Staal is about to have him killed.

The Doctor tells Col Mace about the way the Sontarans stop the bullet’s from firing and Mace thinks he has a way around it.
Alone at last, The Doctor phones Donna and tells her that he needs her to go out into the Sontaran ship and reactivate the teleport links even though it may mean her being captured and killed. He tells Donna that he will talk her through what she has to do starting with disabling the guard outside the door. He then tells her what to look for but cuts short his call when Col. Mace returns and summons him and the clone Martha outside.

Col. Mace shows The Doctor new bullets which contain no copper and should therefore be immune to the Sontarans jamming device. He gives a stirring address to his troops and then calls in the UNIT Airship ‘The Valiant’ ( The Sound of Drums) which uses its engines to clear away the gas from the factory area before opening fire and beginning the battle between the UNIT forces and the Sontarans.

The Doctor and the clone leave the battle and using The Doctor’s sonic screwdriver follow the pattern of alien technology to the basement room containing the cloning vat and the real Martha Jones.
The clone pulls a gun on The Doctor and tells him that she is the one who has been stopping the nuclear strikes. He tells her that not only did he know that but he also knew she was a clone and had done so for a long time. He releases the real Martha which severs the link to the clone which collapses dying.
Martha sees her clone properly for the first time and after the initial shock uses the fact that they share memories to prompt the dying clone to reveal what the unidentifiable element in the gas is. As soon as he knows what it is The Doctor realises that the gas is actually clone feed and that the Sontarans are changing the atmosphere of the Earth so that they can use it as a breeding ground for millions of new clone soldiers.

On the Sontaran ship Donna has found the teleport control and reactivated the link, however she has been discovered. The Doctor fixes the teleport in the factory just in time to rescue Donna and recover The Tardis.  Donna, Martha and The Doctor use the teleport to go to the Rattigan Academy where The Doctor finds all the parts he needs to build an atmospheric converter.   Once activated it will set fire to the atmosphere and burn away all the poisonous gas.

Having watched the atmosphere burn and their chance of a new clone world vanish with it the Sontarans begin invasion plans.  The Doctor recalibrates the atmospheric converter to work on Sontaran air.  He knows that as the Sontarans can never accept defeat he will kill them if he has to.
Knowing that he is unlikely to survive he says a brief goodbye and thanks to Donna and Martha and despite their pleas teleports onto the Sontaran ship.

He offers General Staal the chance to leave but Staal tells him that as Sontarans do not fear death he might as well kill them all now. The Doctor hesitates; can he really kill them all, including himself?
On Earth Luke, heeding The Doctor’s final words to do something ‘clever’ with his life, fixes the teleport so that when it is activated he swaps places with The Doctor. Having been betrayed by the Sontarans Luke has no problem in activating the converter and destroying the Sontaran ship.

Later, in The Tardis, Donna asks Martha if she wants to join them but she tells them that she is happy with her life the way it is now. Before she can leave, The Tardis is pulled into flight by an unknown force and is hurtling out of control into space!!!

Written by Deryn Corner