Narcissa Malfoy's decision to betray Voldemort at ... When they were exposed, Dumbledore took the blame for the organization to save Harry from Fudge's wrath. Of course, he got away, but he ...

The Harry Potterseries has a happy ending, in part, thanks to Narcissa Malfoy, but the books and movies don't get too explicit about why Draco's mother lies to Voldemort and saves Harry's life.