The seventh Doctor

Sylvester McCoy
1987-1989
First appearance - Time And The Rani
Last appearance - Survival
 
First Episode

 The TARDIS is attacked by The Rani and makes a forced landing on the planet Lakertya, knocking unconscious, both Mel and the Doctor.

The Rani and her servants, the bat-like Tetraps, invade the TARDIS and finds the Doctor. As one of the Tetrap kneels over him and  turns him over to seek his identity, the Time Lord's features start to change once again as he regenerates in front of their very eyes.

While the Doctor is still unconscious, The Rani brings him to her laboratory and tries to run some tests on him.

Meanwhile one of the Lakertyans comes across the TARDIS and walks inside as the door is open. He takes the still unaware Mel but when she recovers, he accuses her of being a traitor and an alien spy as she is not in their image.

The Rani had previously kept two Lakertyans prisoner in her lab, the leader, Beyus and his daughter Sarn and when Sarn tries to escape, she encounteres a trap set by The Rani hidden into the ground and walking into it, kills herself.

The Rani then takes on the form of Mel before than trying to convince the Doctor that Mel is in fact The Rani. (Still following?) But when the Doctor finally encounteres the real Mel, they soon recognise each other as allies. We then discover that The Rani is in fact an exiled Time Lord who like the Master, travels throughout the universe un-detected. Her plan is to use the universes greatest minds to cause an asteroid, composed of Strange matter, to destroy Lakertya and change the 'History of Time'. She is eventually is stopped but the Tetraps take her to their home planet of Tetreapyriarbus, where she will rule over them forever. The Lakertyans now free, can live lives of their own and the Doctor and Mel depart.

Last Episode

Now with new companion Ace, an underage runaway, who absconded from home to work in space, The Doctor lands In Perivale on Earth, at her request.

She's back to catch up with all the friends that she abandoned but finds out that only one of them is still around.

They both visit  a newly rebuilt Fitness club, where all her friends used to hang out and as

the Doctor leaves, he comes across a strange cat with glowing green eyes, the Kitling of a feline race called the Cheetah People.

The Cheetah People have been transporting humans back to their home planet which is being devastated by war and every fight that occurs, tears apart the planet.
When Ace is transported there, she forms a bond with one of the Cheetah People, kara. before discovering that all of her friend had been taken there also.
Unfortunately for the humans, once they have been on the planet for a while, they become possessed. their eyes turning a yellowy-green  before then forgetting about their past live. Sometimes the transformation is full and the humans become one of the cat population.
Ace's Bond means that although she isn't hostile, she is absorbing and gaining the powers of the people. The Doctor soon discovers that it is The Master that is really controlling the Cheetah People. He uses the already turned Midge, a friend of Ace, to get him back to Earth, where the Time Lord, Ace and her now found friends, track him down. The hunt for him begins, as the Master is slowly turning and has already developed sharp teeth and the ability to hypnotise whole groups of people at a time.

The Master uses his new army to try and kill both Ace and the Doctor but Midge is killed in the ensuing battle.
Kara then appears and frightens the Master's Army away but is also killed when she tries to murder
the Master.
As Ace comforts her dying friend, Kara fully transforms into her true form, a human. The Doctor along with the Master, travel back to the planet,  now almost completely destroyed by fighting. The Master is left there and killed while the Doctor and Ace travel back to the TARDIS.

This is the last full televised adventure featuring Sylvester McCoy Although he returned briefly In the Paul McGann Film (The eighth Doctor) To film his Own regeneration scene.