Weeping Angels - Feast on paradox

‘And most importantly, before they get to either of them.’ The Doctor pointed to the roof of the terraced house from which the young Mark had emerged. It took a while for Amy to realise what he was pointing at. Six stone Angels, perched high on the brickwork like gargoyles.

‘But why are they after him, run that past me again?’ asked Rory.

‘Moths to a flame,’ muttered the Doctor. ‘If Mark succeeds in changing his own past, he’ll create a paradox.

Once you’ve altered your own timeline, the young you won’t grow old to become the old you who did the altering. Which creates all kind of peculiar and nasty side effects, including the release of a vast amount of potential time energy.’

‘Which is what the Angels are after!’ said Amy, keeping her gaze fixed on the Angels on the rooftop.

‘Exactly. Look at them. They’re hungry, desperate. Then somebody sounds a dinner gong.’

***

Chapter 4, Touched by an Angel