Thankfully for those 4003 people, there was a Time Lord named the Doctor with a vested interest in their survival, a blue time machine and a flair for recklessness when it came to history.
Kazran Sardick sat in his comfortable chair in his comfortable home, watching as the Time Lord visited him in the past. Memories he hadn't known before flooded his mind as his timeline changed. He remembered seeing the fish swimming in the fog for the first time. He remembered the fog shark trying to eat him. He remembered hearing Abigail singing to the shark, the vibrations of her voice settling the fog and calming the shark long enough them to freeze it in stasis and return it to the sky. He remembered every Christmas Eve after that when the Doctor came and they woke Abigail from stasis and had adventures through time and space.
He remembered their last Christmas Eve together.
The Doctor was dressed in a spiffy white suit appropriate for 1960s Hollywood, which was conveniently where they were. He came barrelling towards them along the side of the pool and stopped short when he saw that they were kissing. "Guys! We've really got to go quite quickly. I just got accidentally engaged to Marilyn Monroe. You- have- is- " The Doctor stopped and paid attention. "How do you keep going like that? Do you breathe out your ears? Hello? Sorry. Hello?" They weren't paying attention to him. "Guys! She's phoned a chapel! There's a car outside. THIS IS HAPPENING NOW."
"Yoo-hoo!" Marilyn called from afar.
"Yoo-hoo." The Doctor sighed. "Right. Fine." He resigned himself to the situation. "Thank you, I'll just go and get married then, shall I? See how you like that. Marilyn! Get your coat."
Kazran and Abigail paid him no mind. Kazran was no longer the boy he'd been when the Doctor first came into their lives. Though Abigail had barely aged a few days because of her stasis chamber, she had come to love Kazran as if it had been a lifetime.
Kazran looked like his heart had been broken. After what Abigail had told him, about how sick she was and how little time she had left outside of her stasis chamber, how could he be anything but shattered? "What are we going to do?" He sounded every bit the little boy she'd first known.
"There is nothing to be done."
The old man's chair was no longer comfortable. His house was no longer comfortable. These memories hadn't been his only minutes ago, and now they were as deep and as real as if they'd been there all along because technically they had. Time travel was complicated like that. Kazran tried to argue with the Doctor that he wasn't a changed man, but no one went unchanged when the Doctor decided to play a role in their life.
Today was the last day of Abigail's life. Today was the last day that Kazran remembered being happy. Today was the day that the people of Sardicktown remembered well as being the first day it had snowed in a lifetime, and the start of changes for the better in Sardicktown.
Abigail sang and the pitch of her voice caused the clouds to settle in the sky long enough for the ship to stabilise and 4003 people to land safely. Snow was falling from the sky when Amy and Rory found the Doctor playing with a snowman. At the sight of them, he allowed himself to show more relief than he usually did when people he was fond of almost died.
Soon it was time to head out of the snow and into the TARDIS.
"Right!" the Doctor said, clapping his hands together. "Come on then, let's go."
Rory was all too happy to oblige. "Got any more honeymoon ideas?"
"Well, there's a moon that's made of actual honey. Well, not actual honey and it's not actually a moon technically, it's alive, and a bit carnivorous but there are some lovely views."
"Yep." Rory was clearly unenthused. "Great. Thanks." He headed into the TARDIS, leaving Amy and the Doctor outside for a moment.
"Are you," Amy asked, then hesitated. "Are you okay?"
"Of course I'm okay. Are you?"
"'Course. It'll be their last day together, won't it?"
"Everything's got to end some time, otherwise nothing would ever get started."
Rory swung the door open, interrupting their nice moment. "Uh, your phone was ringing. Someone called Marilyn. Actually, she sounds like THE Marilyn."
"Tell her I'll phone her back and that was never a real chapel."
A moment later, Amy and the Doctor were alone again. "Where are they? Kazran and Abigail?"
"Off on a little trip, I should think." He looked up at the sky where he knew them to be.
"Yeah...Christmas!" Amy gave up on getting a straight answer and entered the TARDIS. "Halfway out of the dark."