Doctor Who Series 10: 7 Big Questions After 'Knock Knock'

This episode more than any other so far in series 10 throws up plenty of questions about the logic of the plot. Why didn’t the mother recognise her son? How did the students come back from the dead? Why did the landlord need to feed the creatures in order to keep the mother alive? All of which could be explained by the unknown alien powers of the ‘lice’. But one puzzle remains - why had no one apparently noticed that every twenty years the occupants of the house had gone missing without a trace?

Perhaps one of Doctor Who’s biggest cop-outs could be employed here – the human propensity to forget and to deny the inexplicable. It’s an explanation used by the Doctor in Thin Ice, and he numbers it among our superpowers (In the Forest of the Night). According to the Doctor if we didn’t forget then the human race would have died out long ago given the pain of childbirth.

But elsewhere in Knock Knock the Doctor appears to have rejected another superpower he once praised the human race for – our propensity to be afraid of danger (Listen). When it comes to being trapped inside an alien ridden house, fear is a useless response. Perhaps forgetfulness is another one of those powers that in certain circumstances can do us more harm than good.