The Chosen One and The Half-Blood Prince

Severus Snape was discovered as a spy mere days before the start of the school year. Thankfully, Albus had been working on a vague contingency plan for this possibility. It had been inspired by the question, "What would it take for Severus Snape to see that he was wrong about Harry Potter?" The answer? Force Severus to go undercover as Alfonse Hopkirk, a sixth year Gryffindor.