Human Nature (Doctor Who Episode) - Plot

Plot

The Doctor and Martha narrowly escape an attack by the Family of Blood who are seeking the Doctor's Time Lord life force to prevent themselves from dying out. As the Doctor directs the TARDIS to Earth, he tells Martha that he must transform into a human for three months to escape the Family's detection while they die, and gives her a list of instructions to follow. He then uses the Chameleon Arch to transfer his Time Lord configuration to a fob watch which he asks Martha to guard.

After landing on earth in 1913, a year before the Great War, the Doctor adopts the persona of John Smith, a schoolteacher at Farringham School for boys, while Martha acts his maid. John's personality is nearly opposite of the Doctor's, being quiet and timid, but faint memories of the Doctor slip through in dreams, appearing as text and images he writes in his "Journal of Impossible Things". Though John carries the fob watch, the perception filter that it possesses prevents John from being curious about it. John has become infatuated with the new school nurse, Joan Redfern, and shares his journal with her; Martha remains concerned, as the Doctor did not instruct her what to do should he fall in love. Timothy Latimer, a younger student at the school with extrasensory perception, discovers the fob watch and pockets it for himself, unbeknownst to Martha.

Meanwhile, the Family of Blood have been able to track the Doctor to Earth, and cover their ship in an invisibility shield to keep it from being discovered. The various members of the Family seek out human victims to possess, including one of the school's prefects, one of Martha's fellow maids, a farmer, and a young girl with a balloon, allowing them to seek out the Doctor undetected. When Timothy briefly opens the watch and experiences portions of the Doctor's memories, the Family detects its presence at the school, and soon recognises Martha. They try to get information from her about the Doctor. Martha realises that the Family has found them and attempts to retrieve the watch in order to bring back the Doctor, but cannot find it. She talks to John and tries to awaken the Time Lord persona, but instead causes John to become angry with her, forcing her out of his chambers as he prepares for a village dance with Joan that night. At the dance, Martha again tries to persuade John to become the Doctor by showing him elements of his past such as his sonic screwdriver, but is unaware that the Family has overheard her conversation. Now aware that John is the Doctor, the Family captures both Martha and Joan. The cliffhanger ending leaves the Family asking John the question of "Maid or matron, your friend or your lover. Your choice."