The Family of Blood
Roots: This story is a direct adaptation of the novel Human Nature. We hear the hymn He Who Would Valiant Be.
Goofs: There's a weather continuity error when Daughter of Mine is looking out the school window it is raining heavily. In all the other shots around there, it is entirely dry. Also, in the scene where she kills the headmaster, her balloon keeps switching hands.
How does Joan conclude that the family getting hold of the watch will lead them to live forever, to breed and conquer, and make a war across the stars from reading the journal (which is a collection of half-remembered bits of the Doctor's past)? She says it's because she read the journal to the end, but it seems really weird that this would just happen to be the most recently written parts of the journal.
If the Doctor can hide himself by "smell ventrilogquism", why did he need to become human in the first place? For that matter, why not just hide in the TARDIS? The family seem incapable of detecting it on their own. Of course, given how easily he beats them, the idea that he should feel the need to hide from them seems ridiculous.
Technobabble: The scarecrows are made using "molecular fringe animation". Tim has a "low level telepathic field" caused by an "extra synaptic engram". Hydrokinometer.
Dialogue Triumphs: Hutchinson: "Latimer, you filthy coward."
Latimer: "Yes sir, every time."
Timothy's description of the Doctor: He's like fire and ice and rage, he's like the night and the storm and the heart of the sun, he's ancient and forever, he burns at the centre of time, and he can see the turn of the universe. And he's wonderful.
Smith: "He won't love you."
Joan: "If he's not you, then I don't want him to."
Mother of Mine: "He didn't just make himself human. He made himself an idiot."
Son of Mine: "Same thing, isn't it?"
Joan: "If the Doctor had never visited us, never chosen this place on a whim, would anyone here have died?"
Continuity: Smith's backstory has him living on Broadmarsh Street in the Radford Parade area of Nottingham.
The watch appears to be sentient, telling TIm when it is time to open it, and is able to detect the family of blood. It also gives him glimpses of his future, where he goes on to fight alongside Hutchinson in the Great War, which allows him to save both of them from dying. Tim is able to hear the watch because he was born with a low level telephatic field. It gives Smith and Joan a vision of what their life could be like if Smith stayed as a human.
The family's limited lifespan can be extended by consuming a Time Lord. Father of Mine suggests that the point of their hunt for the Doctor is that Son of Mine can "live forever".
The Doctor defeats the family by making them immortal. He wraps Father of Mine in unbreakable chains forged in the heart of a dwarf star, imprisons Mother of Mine in to the event horizon of a collapsong galaxy, traps Sister of Mine inside every mirror ever - she manifests by being something you see if you see something move behind you for just a second - and he visits her once a year, every year, and traps Son of Mine in time, setting him to work standing over the fields of England as a scarecrow. He has a way of disguising his scent so that he smells like a human, rather than a Time Lord.
Links: Human Nature (TV). The chains may be a reference to Dwarf Star Alloy (Warriors' Gate.
Extras: This story has an episode of Doctor Who Confidential. The BBC website had an online commentary and a behind the scenes video podcast.
Location: The night of Tuesday 11th November 1913 and morning of Monday 12th November 1913; the Western front a couple of years later; November 11th, several decades later; three other unspecified times and locations
The Bottom Line: "God, you're rubbish as a human." A solid finale. The scenes preparing for the battle build up the atmosphere brilliantly, and Tennant's depiction of Smith, the Doctor, and the Doctor pretending to be Smith
are very good. It's just a shame that the climax completely undermines the premise of the story.