Title: Backwards Compatible
Author name: Ruskbyte

Disclaimer: This story is based on characters and situations created and owned by JK Rowling, various publishers including but not limited to Bloomsbury Books, Scholastic Books and Raincoast Books, and Warner Bros., Inc. No money is being made and no copyright or trademark infringement is intended.

Summary: After decades of fighting, the war is over. Voldemort won. The light's last hope is a desperate ploy, concocted by an insane genius, that probably won't work anyway. Now, armed with an experimental tool whose limits even its creator didn't imagine, Harry must find a way to win a war he's already lost once before.

Author's Note: Inspired by Quantum Leap, the Terminator and all those wonderful Ion Frigates I had a propensity for collecting in Homeworld.

Chapter One
~ Coming Back Home~

Harry Potter had been exceptionally quiet during the trip from King's Cross station to number four Privet Drive. As a point of fact he was usually so when in the presence of the Dursleys, having learnt many years ago that the easiest way to get along with his so-called family was to keep his mouth shut and speak only when spoken to. That way, if he was lucky, they might forget he even existed and thus not bother him.

This start of summer, however, Harry was preoccupied.

The reason for this was that Harry's Godfather, Sirius Black, had died in an effort to safeguard Harry's life during a botched adventure at the Ministry of Magic building several weeks before. It was the fact that Harry and his friends had been at the Ministry in a misguided attempt to rescue Sirius from Voldemort's supposed clutches which weighed rather heavily on Harry at the moment, as it had been revealed that Sirius had never been in any danger and the entire event had been a trap set and sprung by Voldemort.

Sirius had died trying to get Harry out of a trap of his own making and, despite everyone's insistence that it wasn't his fault, Harry knew that he alone held the blame. It had been his pride and ego that made him refuse to resume his Occlumency with Snape. It had been his naive idiocy that blinded him to the possibility that it was a trap. It had been his courageousness and accompanying hero complex that made him charge off half-cocked. It had been his stubbornness and damn fool ego that made him ignore Hermione's warnings. It had been his weaknesses that led his friends and loved ones into a situation where they could not help but be hurt.

Hermione, Ron, Ginny, Neville, even Loony Luna Lovegood. None of them had escaped the battle in the Department of Mysteries without injury. Hermione especially had been grievously hurt and, from what he heard later, had hung precariously in the balance before being stabilized. If the curse which stuck her had been the smallest fraction more powerful she could have been killed.

Just like Sirius.

Besides being a showcase for his weaknesses, his stupidity, the fight at the Ministry had revealed something else. Something that Harry had long tried to deny. Something that he had not thought himself capable of having. Something that, quite frankly, scared him almost more than anything he had ever experienced.

Harry had a dark side.

And it was very dark.

He was not unaware of the similarities between himself and Tom Riddle. Not just the physical similarities, but the stark parallels of the lives they had led. Both losing their parents at a young age. One to murder, the other to abandonment. Both taken in by people that despised them and who they, in return, despised. The Dursleys, an orphanage. Both willing to do whatever to took to remain in the one place they felt at home; the Wizarding World. Both driven by ambition and a thirst to prove themselves...

The motion of Uncle Vernon's car pulling into the driveway of number four Privet Drive shook Harry from meandering thoughts. The Dursleys had completely ignored Harry for the duration of the journey from the train station and their arrival at Privet Drive did not change anything. As a group they exited the car and proceeded quickly into the house, leaving Harry by himself to gather and carry his trunk, Hedwig's cage and his Firebolt.

Staggering through the front door he found himself facing Uncle Vernon, who stood before him like a grotesque caricature of a welcoming committee. Somehow, Harry got the feeling that he was not going to enjoy the forthcoming conversation.

"Now listen here, boy," Vernon began, his face a particular shade of red that Harry knew meant he was towards the higher end of his lower range temper. Eskimos had a hundred words to describe snow. Harry had a hundred shades of red, ranging from dusky pink to a lurid purple, to describe Vernon's anger.

Settling his trunk and other items down, Harry prepared himself for what would no doubt be an exceptionally boring and often repeated lecture about how magic was abnormal and would not be tolerated in the Dursley household under pain of death. Vernon had just taken a deep breath in preparation to deliver his lecture when something very peculiar happened that stopped Harry from ever hearing whatever it was his uncle had to say.

The universe sneezed.

At least, that's the only way that those who experienced it could describe the sensation. If they had been fanciful people, which Vernon most certainly was not, they would perhaps have almost heard the universe going "Ah - ah - ah" as everything seemed to grow dim around them in the entrance hall. Then, with typical explosive suddenness, came the "Choo!"

The result, much to Vernon's surprise, was that Harry was suddenly lying sprawled on the house floor. His eyes were free of his glasses, which had been knocked askew and completely off his face as he fell, and he was staring blankly up at the ceiling. For a moment Vernon thought that something had happened and his nephew had dropped dead because of it. He didn't know whether to be worried or thrilled by this, but it proved to be a moot thought as he realized that Harry was still very much alive.

It was unsettling though, the expressions flitting over his face and in his eyes. They came and went with mercurial speed, barely long enough to be seen before melting away and being replaced by something new. At first Harry seemed to stumble back and forth between horror, despair, grief and a multitude of similar emotions. Slowly, however, this changed. Anger, fury and an undiluted hatred flickered in his emerald eyes, though his features had begun to settle into an implacable calm.

After nearly five minutes, in which Vernon could not bring himself to move, Harry's face was a blank mask that seemed to be almost carved from stone. He pushed himself up into a sitting position and appeared to stare into space for a long time, his eyes as blank and empty as his countenance, though they darted back and forth, focused on and following something that only Harry could see. Slowly, like a bank of thunderclouds gathering on the horizon, a terrifyingly hard and cold determination began to form and solidify in Harry's eyes.

When Harry finally turned his burning gaze towards Vernon, the stocky man unconsciously stepped back until he was pressed up against the wall behind him. This was the look of someone that could kill, who had killed. And when he did, it would be without any compassion, without any remorse and entirely without mercy. With alarming clarity Vernon realized that he was in the presence of a person that could calmly and efficiently kill him with complete indifference.

And then something even more alarming happened. A dark fire lit up behind Harry's eyes and his lips curved into a dangerous smile.

For the first time in his life Vernon Dursley was deathly afraid of his nephew.

And it had nothing to do with magic.