Harry has a retarded son called Albus Severus who joins Slytherin house and befriend's Malfoy's gay son, Scorpio, which causes Harry to despise him.
Harry's favorite son James gets a new broomstick for Christmas but Albus gets Harry's orphan baby blanket because symbolism. This makes Albus despise Harry because everything is always about Harry.
Albus and Scorpio encounter Cedric Diggory's dad who is heartbroken at his son's death, Cedric's hot female teenage cousin convinces them to steal a Time Turner from Hermione who is the first black female Minister of Magic.
They go back in time and save Cedric by humiliating him out of the Triwizard Tournament, but turns out that they turned him emo and he becomes a Death Eater who helps Voldemort win. Oh and his hot cousin is actually Voldemort and Bellatrix Lestrange's secret daughter in disguise.
With Albus erased from time and Voldemort victorious, Scorpio is now the "King" of Hogwarts due to his family connections, but he is so gay that he goes back in time again to fix everything.
It ends with Harry and Albus respecting each other because it's the end of the play.
OK... maybe it is a bit shit. It will have to be two or more movies since the play is actually two plays back to back due to the length.