S03E08: 'Human Nature'

Under attack and rushing into the Tardis, The Doctor tells Martha they must take desperate measures to avoid the enemy until they reach the end of their life span. This involves the Time Lord altering his DNA to become human and put his pursuers off the Gallifreyan scent. He will have no knowledge of his past and it’s up to Martha to blend in to the time zone and look after an invaluable pocket watch that – once opened – can restore The Doctor to his former self.

We then discover that the plan is in operation in 1913 Britain, with The Doctor now known as John Smith – a teacher – and Martha as his maid. Smith is falling in love with the school matron Joan and shows her a notebook where he has sketched some very strange dreams he has been having – featuring blue boxes, aliens and a girl called Rose.

Martha notices a strange green object in the sky heading towards the nearby countryside. Simultaneously, a schoolboy called Jeremy has headed into the woods to retrieve a stash of beer. He comes across the newly landed spaceship, partially invisible, and enters. He is soon taken over by the unseen inhabitants – The Family of Blood. Activating an army of scarecrows to gather other humans such as teacher Mr Clark and little girl Lucy, the Family all soon have human form and head off to hunt down The Doctor.

The Family believe they are onto the scent as unknown to Martha or John Smith, a psychic pupil called Latimer has taken the pocket watch and opened it – putting out some Time Lord essence into the air.

John Smith, after briefly displaying his past skills by saving a young mother and child with a cricket ball, attends a dance with Joan. By now, Martha is worried that he is falling in love with her, but an instructional video made by The Doctor made no mention of what to do in that scenario.

The Family storm into the dance alongside their scarecrow army. They demand that John Smith reveal his true Time Lord self and take both Martha and Joan hostage. They demand that he chooses one of them to save and one to kill