‘Before the Flood’ opens on a narration from The Doctor questioning how the classic time travel concept of predestination paradoxes, where the events of the present can only exist by someone time travelling to the past. The Doctor uses the example that he time travelled back in time to meet Beethoven but inadvertently made him famous by presenting him with his first sonnet. This got me slightly excited for the idea of an episode that explored this concept, however it is simply introducing the idea that will be brought up again in the episode’s climax.
It was fitting then, that the One who loved us first should seek to redeem us from our pride by humbly taking our human nature to Himself as the Incarnate Word, and, as man, subject Himself to a death of love under a different tree, thereby redeeming that which was lost under the tree in Paradise and restoring to us again the possibility of attaining to mystical union with Him.
The Human Pattern Recognition Machine | Sapient Paradox
Unfortunately the alien creature’s plot, if you can even call it that, amounts to nothing and The Doctor saves the day with a ridiculous solution involving the sonic glasses (which are sadly still a thing). The Doctor reiterates his message about predestination paradoxes but little is done to solve the mystery presented. Perhaps this will be a plot point in future episodes but it seems more likely that it will amount to nothing, making this storyline a complete waste of time.