Sort of inverted Severitus. Harry's world is turned upside down at the start of First Year when it is revealed that he is the son of James Potter and not Severus Snape. Now into Fourth Year.
Harry arrives at Grimauld Place to spend the remainder of the summer with Lupin. But something in his OWL results changes everything. Time travel. Possible minor spoilers.
New summary: The story of Harry's struggle to live a normal life in spite of fate and Dumbledore.