(A/N: I don't own Halo, Doctor Who, or Harry Potter… of course)

Set:

Harry Potter – between Half-Blood Prince and Deathly Hallows

Doctor Who – between The Shakespeare Code and Gridlock

Halo – between Halo 2 and Halo: Uprising

Chapter One – The Beginning

Harry looked around at the DA members. He was intensely proud of them all – especially the ones who had been loyally by his side during the Ministry crisis. He knew they would not fail him in the latest crisis…

Harry and the other DA members were seated at their respective tables, waiting for Professor Dumbledore to speak. There was a lot of talking – until suddenly, Dumbledore's aged but clear voice rang out.

"There is a new threat to the wizarding and Muggle worlds alike. This threat is on the level of Voldemort himself – but unlike him, does not seem to be taking an active interest in Hogwarts and its students," (at this point his eyes rested on Harry for a second), "this threat is of an ambiguous nature. We don't know what it is doing. We just know that we have to be ready."

Harry knew that whatever happened, the DA would always be on the right side. They would never fall to the new threat.

A familiar blue police box materialised, and the door swung open. The Doctor confidently strode out – like he always did. He stuck his head back in, and yelled to the other occupant "Come on, there's a whole new world out here!"

Martha Jones walked out of the TARDIS, rubbing her eyes. She looked around, and wondered if she'd really slept that long – it was definitely night. Then she remembered that the TARDIS travelled in time.

"What the hell did we hit?"

They'd hit something in the process of materialisation, but whatever it was, it had gone.

"I'm… not sure. But the TARDIS always shows us when there's mischief about – you think the thing we hit might be the mischief we were 'seeking'?"

Martha wasn't listening. Her eyes had locked on to a rather familiar-looking castle in the distance.

"You have got to be kidding me."

"Well, what do you know, looks like we jumped a time track. This could be fun."

Martha's eyes had locked on to the shape familiar from so many movies – Hogwarts Castle.

Suddenly there was a blue glow off to their left and a strange noise. The Doctor immediately jogged off to investigate, hurrying Martha, who was still staring at the castle, along with him.

The Master Chief looked sceptically at the blue portal that the escaping 2401 Penitent Tangent had rigged up for him. In Gravemind's attempt to capture Cortana, he had let go of his other prisoners: the dead Prophet of Regret, and the very much alive 2401 Penitent Tangent. Tangent had flown up to High Charity, and hidden onboard the Ark.

Tangent claimed that the portal would return the Chief to Earth, and urged him to step through. What the Chief could see through the portal was a small, rather old village. He thought What the hell, I can just catch a ship back to Sydney HQ, and made up his mind to step through.

A strange twisting sensation immediately took over, and the Chief felt like he was falling for a second, then he landed on his feet in a dark alley. The portal made an odd sucking noise, then disappeared in a bright flash of blue light. The Chief thought, Great, that's gonna wake the entire goddamn village up.

Oddly, his suit sensors were indicating a strong, fast data access line to the suit, from a source somewhere about five hundred metres to his right. He had a moment of panic thinking someone was hacking the suit – then realised there was nothing coming through the connection. He probed it and discovered a completely different set of data access protocols – definitely not UNSC. Intrigued, he walked out of the alley; that was when he saw the difference. The entire town looked like something out of a history program.

What looked like old petrol-fueled cars were parked on both sides of a bitumen road, next to houses with what the Chief considered to be five-hundred-year-old architecture. Frighteningly, everything looked new.

The only conclusion he could come to was that the blue portal had somehow transported him back in time. Either that, or Penitent Tangent had pulled the wool over his eyes in a very odd way – which didn't seem likely.

The Chief heard quick footsteps off in the direction of the access feed – he looked and saw the silhouettes of a man and a woman off to his right. His suit camera systems brought up a picture-in-picture of the data feed source – a rather battered blue wooden box about three hundred metres behind them. Then, his eyes snapped to the open door panel on one side of the box, where he could see an impossibly large space inside. Really impossibly large. That can't be right, was the only thought that could get into his stunned mind. He stared for ten seconds, then snapped out of it as the man and the woman jogged up to him.

The man didn't seem taken aback by his appearance, and stuck out his hand.

"Hi. I'm the Doctor. And this is my friend, Martha."
The girl this "Doctor" person had identified as Martha was covering her shock rather expertly – you don't tend to see an eight-foot-tall green man every day, not five hundred years ago.

"SPARTAN-117, UNSC, on duty with the 57th ODST 'Helljumpers' division. Mind answering a couple questions, sir… no matter how stupid they sound?"

"What kind of questions?" the Doctor asked, with a rather challenging tone… but the Chief was too tired to care.

"Like, where am I? What date is it? What time is it? That sort of questions."

"You're in the small village of South Hogsmeade, Britain, and it's 11:49 pm, eighth of July, 2007."

"Crap. That's Monitor transport for you."

"These wouldn't be the Forerunner monitors, would they?" asked the Doctor quietly.

"What the… How did you know?" asked the Chief, stupefied.

"I've seen a lot. Now, I think we'd better get going toward that castle over there."

The Chief's initial impulse was to stay where he was – but the Doctor seemed to have an aura of power. He decided to stick with the Doctor – if he was the owner of the physics-defying blue box, he might be able to answer some of the Master Chief's other questions. Or at least that was the excuse he gave himself.

(Please R&R, this is my first story).