Trope mix. Harry gets sent back in time after the time turner is broken at the end of his third year. How far back who knows. Harry knows he needs to keep a low profile to keep the future even relatively normal even if that means letting his parents die. He gains immortality (Vampire Harry?) to be able to return relatively young. The silhouette that cast the patronus was in fact immortal Harry.
Harry’s name comes from the Goblet of Fire. People are understandably confused since he’s not been seen since the end of last year.
Harry now has a chance to finish what was started as a young boy and completely demolishes Voldemort. The real challenge begins as he tries to settle down and have a proper life after spending so much time trying not to mess with time, as well as the fallout of what occurred.