7 Great Harry Potter Plot Twists That Don’t Get Enough Credit
2. Harry Learns The Truth About Snape And The Prophecy – The Half-Blood Prince
At the end of The Order of the Phoenix, Harry learns about the prophecy whilst in Dumbledore’s office. The content of the prophecy is discussed, and the fact one of the Death Eaters overheard Trelawney’s original foretelling.
However, Dumbledore does not tell Harry the Death Eater in question was Severus Snape.
In The Half-Blood Prince, Harry discovers the truth after a conversation with Trelawney, and he is understandably outraged at the headmaster for keeping this information away from him.
Yet the real strength of this twist is how it links to Snape’s character arc, the bulk of which is unveiled towards the end of The Deathly Hallows when Harry witnesses Snape’s memories in the Pensieve.
In essence, the information Snape passed to the Dark Lord resulted in the death of the woman he loved – Lily Potter. Snape, therefore, was burdened with guilt after Voldemort attacked the Potters, and as such, his decision to protect Harry throughout the series was his way of dealing with said guilt.
It's just a shame this extra layer of depth didn’t make it into the movies.