Doctor Who-The Poison Sky

                     Even though Sylvia is successful in breaking Wilf out of her gas filled vehicle before he asphyxiated,the poisoning gas emitted by the ATMOS vehicles is saturating the air of all major cities on Earth in a chocking pillar of smoke. With Wilf's encouragement, Donna has gone off with the doctor,who asks her to go to the TARDIS alone-which in turn is transported to the Sontaran vessel in Earth orbit. Meanwhile the news media reports urban dwellers fleeing en mass to the country side while they those remaining are instructed to stay inside. UNIT itself is trying very much in vein to stop the crisis. But the doctor continues to resist their insistence on using force in the matter. Without a proper sample of the gas in hand, UNIT feel forced to act and decide on a strategic nuclear strike against the Sontaran ship. Each time the strike is attempted,it is instantly shut down. Meanwhile Luke Rattigan tries to explain to his fellow school mates at the Academy the Sontaran's plans to place them all on another world where their intelligence will come in use. They dismiss him as insane and promptly abandon him. The doctor meanwhile tries to face down the Sontaran's by UNIT communications-pointing out that the gas goes against their strategies,having weapons that could easily destroy the planet they would'nt need a biological device. 

                    Of course he also learns their 50,000  year old war with the Rutans has been going badly.  When a sample of the gas is finally obtained using UNIT's enormous new atmospheric vessel, the doctor follows Martha to the lab where he reveals he was aware of her cloning,and of her sabotaging all attempts at a nuclear strike against the Sontarans. Transported on board the Sontaran ship himself, Rattigan learns he was only being used by the Sontarans to develop the technology needed for their plan and is dismissed to Earth,crestfallen. And the doctor has already figured out their plan when the cloned Martha dies and reveals the gas emitting from the ATMOS vehicles contains the same material used in Sontaran cloning method,and they are planning to use the planet as a hatchery to produce more warriors. The doctor is able to use an atmospheric condenser to fumigate the atmosphere of the poison gas. Of course this is after Rattigan usurps the doctors attempts to sacrifice himself to destroy the Sontaran ship-taking his own life to protect the doctors. After this Donna departs with the doctor and Martha,not intending to join them,is forced to when the TARDIS is locked and pulled away from the planet.

                  One of the main factors of this particular story is how much it points to the nobility of the doctors character. For a good half of it, he feigns complete ignorance and uncertainty that Martha is a clone attempting to facilitate the Sontaran take over of the planet-in order to stave of UNIT possibly destroying the Earth with a nuclear attack. Luke Rattigan points to the type of genius level intelligence enveloped by his own resentment at being misunderstood by other people. He hopes for a world where he and others like him will be left alone. Driven to tears when the Sontaran deception is revealed, he willingly sacrifices himself to destroy the enemies he never realize he had so the doctor,who he learns is the real hero of this affair, will continue to survive and triumph. Though Donna and Martha are both complimentary in helping the doctor in this story, though Martha is presented in her cloned form most of this part of it, Martha wishes to stay behind. Even though,as is typical with the doctor things don't quite end up as expected.