The Doctor looked up at a streetlight and saw tiny fish swimming around it like moths. "Fish!"
"Sorry, what?" Amy asked over the communicator.
"Fish that can swim in fog. The air is thick enough that fish can swim, meaning . . . ." The Doctor's feet floated gently off the ground with barely a thought. "Yes!"
"Doctor . . . ." Amy said.
The Doctor drifted forward with a gentle wave of his arms. He set his feet, pumped his arms, and launched himself into the air. He shouted and laughed as he continued flying upward without much more effort. He spread his arms and flew around above the buildings. It was the strongest, smoothest air he'd ever felt. He slipped through the air like a hot knife through butter.
He was snapped out of his happy trance when he heard Amy on the phone again. "Doctor! Doctor! Please don't get distracted!"
He held the phone up to his ear and began to glide downward. "Sorry! This air is wonderful! I can get off the ground with a simple thought! I can stay in the air with only one arm! I love new planets!" He dove back down to the ground and floated toward another streetlight to continue his investigation of the fish. "Now why would people be frightened of you tiny little fellas?" He held out his hand and the fish swam around his fingers. "Look at you, sweet little fishy-wishies. Mind you, fish in the fog, so the cloud cover . . . . Ooh. Careful up there." He thought he saw a large shadow appear in the fog and fade away, and realized how dangerous his little flight had been.
The Doctor opened the door and drifted into the room behind Kazran, transfixed by a video on the wall. Kazran as a young boy in the video cried on the desk, hiding his face.
The Doctor tried not to fly stiff and straight like a wraith, more smooth and friendly like Peter Pan. He floated behind Kazran and let his feet touch the ground as he lay a hand on Kazran's shoulder. "It's okay. It's okay."
Kazran jerked away from his touch, spinning to face him. "What have you done? What is this?"
"Found it on an old drive." The Doctor pushed off the ground and floated gently around. "Sorry about the picture quality, had to recover the data using quantum enfolding and a paperclip." He picked up a newspaper as he drifted by and lay on his back to read it. "Oh, I wouldn't bother calling your servants, they quit. Apparently they won the lottery at exactly the same time, which is a bit lucky when you think about it."
"There isn't a lottery," Kazran said.
"Yeah, as I say, lucky."
"There's fog warning tonight," Kazran's father said on the video, "You keep those windows closed, understand? Closed!" Kazran's father moved to close the windows.
"Who are you?" Kazran challenged.
"Tonight, I'm the Ghost of Christmas Past," the Doctor answered.
"Mrs. Mantovani will be looking after you tonight," Kazran's father said, "You stay here till she comes. Do you understand? Do you understand?!"
"How do you . . . do that?" Kazran asked, backing away from the Doctor, "Flying about like a . . . like a . . . ."
"Like a fish?" the Doctor finished. He turned upright and floated toward Kazran. "Did you ever get to see a fish back then, when you were a kid?"
"What does that matter to you?"
"Look how it mattered to you."
"I cried all night and I learned life's most invaluable lesson."
"Which is?"
"Nobody comes. Get your feet on the ground! Stop flying about! Nobody can fly."
"Yes they can. I can fly. You can fly. What do you think of that, Kazran? You can fly, just like the fish. The air on this planet is built for flying. You love the fish. You're always thinking about the fish. The fish are a part of you. The fish can fly, and so can you."
Kazran seemed almost hypnotized, listening to the Doctor, wishing he could fly. He suddenly looked down and saw that he was a few inches off the ground. His feet hit the ground hard. "Get out! Get out of my house!"
The Doctor quickly floated backwards toward the door, colored by the video projection of Kazran's past. "Okay, okay. But I'll be back. Way back. Way, way back." He bumped into the door, then turned around and opened it and finished floating dramatically backwards out of the room.
The Doctor held the reins of the shark as it flew through the clouds, carrying Abigail and a young Kazran with it.
"How are we going to get back?" Kazran asked.
"I don't know!" the Doctor yelled over the wind.
"Do you have a plan?" Abigail asked.
"I dunno!" the Doctor yelled.
They all laughed and shouted as the shark took them on a wild ride above the city. The Doctor quickly let go of the reins, reached back to grab Abigail and Kazran, and flew out of the seat. He flew beside the shark, pulling Abigail and Kazran with him. The shark snapped at him and he pulled away. The shark flew away.
Abigail burst into song and let go of the Doctor's hand, flying beside him. The Doctor hadn't thought it was possible, but the vibration of the crystal molecules in the air made it ever easier to fly. Kazran slowly let go of the Doctor's hand and flew on his own. A huge grin of pure joy spread across his face. Joy so joyful he couldn't shout or laugh. He could only smile with shining eyes and pure bliss.
The Doctor floated in the vault, watching Kazran looking at Abigail in her cryo chamber.
Kazran suddenly noticed him. "Doctor!"
"I'm sorry. I didn't realize," the Doctor said.
"All my life, I've been called heartless. My other life, my real life, the one you rewrote. Now look at me."
"Better a broken heart than no heart at all."
"Oh, try it. You try it. Why are you here?"
"'Cause I'm not finished with you yet." The Doctor floated forward, stiff and straight like a wraith. "You've seen the past, the present . . . and now you need to see the future."
"Fine! Do it! Show me! I'll die cold, alone, and afraid. Of course I will, we all do! What difference does showing me make? Do you know why I'm going to let those people die? It's not a plan. I don't get anything from it. It's just that I don't care. I'm not like you. I don't even want to be like you! I don't and never, ever will care!"
"And I don't believe that."
"Then show me the future. Prove me wrong."
"I am showing it to you. I'm showing it to you right now. So what do you think?" the Doctor finished, looking past Kazran at Young Kazran standing behind him.
Kazran wrapped his hand around Abigail's as she continued to sing. They watched the people coming out of their homes to marvel at the snow. The children began to play. Abigail laid her hand on Kazran's cheek, still singing. They looked up to see the shark swimming above them.
"Hello, my old friend," Kazran said.
"Let's go," the Doctor said to a young Kazran.
Kazran as a child walked into the TARDIS. The Doctor smiled at his handiwork before stepping inside and closing the door. Kazran and Abigail waved as the tall, blue box slowly vanished. Kazran closed his eyes and took a deep breath, thinking about the fish. He remembered the Doctor's flying lessons every Christmas Eve. He remembered the first time he really flew, the time the shark took them on a trip in the clouds. He remembered when the Doctor barged into his house and told him he could fly. He opened his eyes and looked down. His feet were off the ground, and so were Abigail's. He looked up at her, singing with a smile. He smiled back and they flew into the air together. Their last day together.