Chapter One:

A hoard of aliens invading from a Tesseract-induced hole in the ozone layer, no problem. A crazed, megalomaniacal Demi-God threating the plausible enslavement of the human race, piece of cake. The sudden and unexplainable arrival of a man in a blue Police Box claiming lordship over time and space, slightly more difficult…

"What you're implying isn't possible, Doctor-" Bruce trailed off, waiting for a name he didn't receive.

"Doctor, yes." The man nodded, crossing his arms authoritatively. "And just because it's unfamiliar doesn't mean it's not possible."

"You're a Doctor of what, exactly?" Natasha frowned, hand not quite leaving the strap on her thigh where Hawkeye knew there to be a substantial supply of collapsible weaponry. He took a step towards her, more for his own comfort than hers.

"Just the Doctor." The man replied matter-of-factly.

"And you're saying you traveled here in that… through space?" Steve tried, the implausibility of it challenging even his level of outlandish acceptance.

"And time," The Doctor winked, more than slightly amused at Steve's blank expression, a sort of odd pride in his voice that seemed common to the man.

"And time…" Steve parroted dumbly, shaking his head. "Doctor… Sir… I don't think-"

"Look, Doc Brown," Tony cut in. "I'm sure you could rig that telephone booth of yours to fly through space. I'm working on a few prototypes myself. But time?"

"It's simple mathematics. Well, that and Gallifrayen engineering, but mostly the mathematics." The Doctor offered happily, words stringing together in practically tangible excitement. "The TARDIS merely calculates a stream of continuously fluctuating algorithms until it pinpoints a designateable variant in a corresponding system that signifies some sort of distress."

All eyes settled at once on the resident geniuses, Tony raising an eyebrow at the subtle shake of Bruce's head. "Whatever that means," Tony sighed, pinching at the bridge of his nose in a way that showed just how little he enjoyed being confused. "The laws of physics are absolute. There's nothing you could do to convince me to-" Any desire to revel in Tony Stark's apocalyptically rare moment of speechlessness was overshadowed at once by the simple snap of the man's fingers and the opening of the blue Police Box's front door.

"Let me guess what you all might be thinking." The Doctor smirked, leaning against the door frame, an expanse of more space than possible stretching into the TARDIS behind him. "Bit bigger on the inside?"

Bruce was the first to move, walking up next to Tony to mumble dazedly into his ear. "You were saying about the laws of physics being absolute?"

"Did I say absolute?" Tony gawked back.

The Doctor grinned, taking a moment to enjoy the spreading revelation before locking eyes with the man who'd been silent through it all. "Nicholas!" Everyone's eyes turned to Fury just in time to watch him frown, displeased at the Doctor's familiar tone. "What happened to the eye?" Fury chose not to answer, crossing his arms like a child giving his parents the silent treatment. The Doctor smirked. "Alright. We'll catch up later. Down to business then. Where's Phil?"

Everyone tensed, some looked away, faces ranging from uncomfortable to sad to angry, all signs the Doctor's years of experience had taught him how to instantly translate. This time, however, it was harder to swallow.

"But that doesn't make sense." Already the Doctor could feel the pull rising, forcing him to pace, to calculate, to plan a way around it, undo it, a desire he so often had to quell against the logic of times beyond his control, but this. This time was different. "What happened?" He asked Steve, the Doctor's demeanor so different from before, so much more focused, almost dangerously so. The Captain straightened to attention like the soldier he was.

"It was Loki, sir." Steve replied matter-of-factly, but the hurt was obvious behind his eyes. The Doctor frowned.

"The Asgardian Demi-God? No, that…" He pinched at the bridge of his nose as if warding off a headache.

Thor took a step forward. "You know of my brother?"

The Doctor waved him away. "All of time and space probably knows about your brother at this point. The guy gets around." He shoved a hand in his pocket and ran the other over his face in frustration. "It would certainly explain the TARDIS' fluctuating distress calibrations… But there's no way-"

"No way what, Doctor?" Bruce cut in, the sound of the scientist's voice seemingly bringing the Doctor back to the present, his eyes locking on Bruce's in what could almost be called concern.

"Phil Coulson's death is a fixed point in time," he answered, taking a step towards the open, waiting doors of the TARDIS, letting the words sit heavily with everyone in the room, sinking in slowly but effectively. "And whatever Loki did wasn't it."

Chapter Two: