(For the sake of my story, Draco has a younger sister …who started Hogwarts late. She's a fifth year, but went to Durmstrang.)Prologue: Traitors!Harry, Ron and Hermione were all sitting in the Gryffindor common room, on the last day of their sixth school year. They had a silencing spell and an invisibility charm over them to insure their privacy. Hermione was lecturing Ron about preparing for the NEWTs and Harry was doing his best to tune them out. Over their sixth year of school, they had all become accustomed to doing absolutely nothing without their wands. They had trained in every spare second to work on defeating Voldemort. Knowing the prophecy, that Harry had to defeat Voldemort, was only motivation to work harder and faster. After Sirius was rescued from beyond the veil and cleared of all the false charges, he'd come to teach DADA.
Sirius and Harry had gotten in numerous fights over the last year, either because Harry was pushing himself too far or not working hard enough, or because, in Harry's words, Sirius was being, 'a rude, inconsiderate, over-controlling jackass!' Everyone was surprised when they hadn't gotten along well, especially Harry and Sirius, both of them having clear pictures in their minds of who the other was. Both of those pictures being wrong. Harry thought that Sirius would be like a cool godfather that would let him get away with anything short of murder and torture, Sirius thought that Harry was an angelic kid who never did anything wrong. That being proved wrong was probably a large part in why Sirius was so quick to believe what happened next.
As Harry canceled the invisibility and silencing spells, five aurors walked into the Gryffindor common room, followed by a tight-lipped, extremely angry looking Professor McGonagall. The room was totally silenced without the use of magic. Everyone stared at the aurors to see where they were going, and pandemonium broke out when they stopped in front of Harry, Ron and Hermione. The three of them looked at each other, obviously completely confused, and the auror who was obviously in charge said, "Harold James Potter, Hermione Jane Granger, Ronald Bilius Weasley. You are under arrest for the murders of Padma and Parvati Patil, Colin and Dennis Creevey, and Draco and Hannah Malfoy."
The three of them just gaped at the aurors. Sirius, Remus and Dumbledore all had disappointed and angry looks on their faces, and Harry was in complete disbelief. These people seriously thought that they killed them?! Ron just looked dumbfounded, and Hermione looked to Dumbledore for help, but found none. As Harry, Ron, and Hermione protested, the lead auror spoke again. "There were witnesses who saw the three of you murder the six of them. Do you have any witnesses for you defense," at the shake of their heads the auror continued, "Due to the heinous nature of your crimes and the fact that you have no witnesses for your defense, you are to be transported directly to Azkaban, where you will serve two life sentences each."
Recovering from his thunderstruck state, Harry said, "Oh, I think not. Have you ever heard of Veritaserum? And what gives you the right to deny us the right to a trial?"
The auror shrugged, "Ministers order!"
Harry just shook his head. "That explains that, then. Obviously, your minister doesn't have any brains or he'd realize that we didn't do this, or at least give us a chance to prove it," Harry turned from the auror to look at his godfather, "Do you believe this, Sirius? I need your honest answer, and I need it now."
Sirius just looked at Harry with his eyes downcast and said, "I don't want to believe you would do this, but I saw you kill them. Therefore, my answer is yes, I believe it."
"That's all I needed to know, then. I believed in you, Sirius, when it counted, why don't you believe in me? I feel this desperate need to remind you how many people saw you kill twelve muggles and Peter Pettigrew. But, whatever. I'm not just going to sit here and let you take me to my worst nightmares, and if you think I am, you've got serious mental issues. Actually, the fact that you believe this utter crap, proves that you've got mental problems." With those final words, Harry grabbed onto both Ron and Hermione and willed his magic to show him to safety, a trick he'd learned recently. As he left, he sent a message to Hogwarts, "You were my home once, but I'm not welcome here anymore, please allow us passage." And she did. That was the last anyone saw of the Terrible Trio as they were renamed (they had been the Terrific Trio) for three and a half years.