The Doctor sighed when Martha went around the outside of the TARDIS again.

"But it's just a box," she muttered, touching the wood. "But it's huge."

By the time she finally reached the inevitable conclusion—It's bigger on the inside!—his patience was wearing thin. It had been a year since he'd really travelled, and that urge to go someplace new was finally returning.

She walked slowly up the ramp, and he shut the door behind her before jogging up to the console. "Right then, let's get going."

Martha circled the console, staring up at the coral struts that supported the cavernous ceiling. "But is there a crew, like a navigator and stuff? Where is everyone?"

Even with another person in the room, the TARDIS felt empty without Rose beside him. "Just me."

"All on your own?"

Something in Martha's voice made the Doctor look up at her, and he flinched from the sympathy in her eyes.

She nodded towards his left hand. "Only, I couldn't help but notice… you're wearing a ring."

The Doctor twisted his wedding band around his finger. "I had… I have a wife. Rose… her name is Rose."

"How long were you together?" Martha asked.

The Doctor sniffed. "We travelled together for almost three years, and were married for a year before she… it was… she's not here anymore, that's the only thing you really need to know."

He could feel the sob building in the back of his throat, and he stared down at the console, determined not to cry in front of Martha on her very first day. It had been a year since he'd lost Rose, and the broken bond still throbbed in the back of his head, a never-ending ache he couldn't do anything about.

"That kiss really was just a genetic transfer, wasn't it?"

The Doctor's head snapped up. "What? Yes, of course! What did you… I told you!"

She held up her hands placatingly. "I get it now," she promised. "But I didn't know before. And I didn't notice your ring until just now."

The Doctor shoved his hands into his pockets. It was tempting to tell Martha he'd changed his mind, to ask her to leave. The last thing he needed to deal with was a companion pining over him.

But Donna's words had stuck with him. After leaving her on Christmas Day, he'd hidden himself away in the TARDIS for months. Finally though, the urge to travel had become too strong to resist, and he'd remembered what Donna had said.

"I think you need someone to stop you."

He looked at Martha, pinning her with his gaze. "Before I met Rose, sometimes I'd take people with me. Friends. That's all this is, Martha. If you're not on board with that, tell me now."

Martha's eyes widened and she shook her head frantically. "I get it, I promise," she assured him.

"Good." The Doctor spun away from her, eager to leave the revealing conversation behind. "Well, then," he said, shoving a switch into the right position, "Close down the gravitic anomaliser, fire up the helmic regulator. And finally, the hand brake. Ready?"

"No," she said breathlessly.

The Doctor grinned at her honestly, then flipped the brake and threw the dematerialisation lever "Off we go."

The TARDIS lurched into flight, and Martha grabbed onto the console. "Blimey, it's a bit bumpy."

He laughed and held out his hand. "Welcome aboard, Miss Jones." Having a companion again was a good idea.

Martha shook his hand. "It's my pleasure, Mr. Smith."

oOoOo

"And then he looked up at the sky, my hand held in his, and he said, 'And it is going to be… fantastic.'"

Rose closed the handmade picture book she'd given Tony last year for Christmas and smiled down at her little brother. "Did that really happen, Rosie?" The little boy's blue eyes glowed with excitement. "Did the Doctor really fight an alien with swords?"

"Just like in the book," she promised him. "He won a sword fight against the bad alien, and they flew away and never came back."

Well, so she'd edited out a few details from the story to make it suitable for a four-year-old. But really, it was true that the Sycorax had never returned to Earth. Tony didn't need to know that was because Harriet Jones had ordered their ship to be blown out of the sky.

"An' then you got in the TARDIS and flew through time and space and trouble was just the bits in between!" Tony crowed gleefully.

Rose laughed. "That's right."

"Tell me again about the planet with the giant flying dinosaurs!" Tony demanded.

A lump rose up in Rose's throat. Like every little boy, Tony loved dinosaurs. But that planet meant more to Rose, because that was where the Doctor had asked her to share a bond with him.

She shook her head. "I'll tell you tomorrow. Right now, it's time for little boys to be in bed." Tony opened his mouth, and Rose raised an eyebrow. "The faster you fall asleep, the faster it'll be Christmas," she told him, repeating what Mum had told her when she was Tony's age.

Tony's eyes widened and he immediately lay down and pulled the covers up to his chin. "I've been a good boy for Santa," he confided. "I didn't even snitch a biscuit from the table earlier, even though Mummy wasn't looking."

Rose hid a smile at his earnest declaration. "Are you hoping for an extra-special present?"

He nodded furiously. "I asked for him to bring the Doctor." He screwed his eyes shut. "Night, Rosie."

Rose was thankful Tony had closed his eyes before he could see the tears well up in hers. "Night, Tony," she managed to say, then she left the room as quickly as possible.

Out in the hallway, she pressed her back to the wall and waited for the ache in her heart to ease. Of course Tony had asked Santa to bring the Doctor. He'd been enchanted with Rose's stories of her brave alien husband for over a year.

Rose sighed and rubbed her temples. The agony of the broken bond had faded to a dull ache years ago, but every once in a while, when the memories were stirred up, it came back.

Footsteps on the stairs warned her that someone was coming. Mum, probably. Not wanting to explain why she'd been crying, Rose turned and walked swiftly towards the stairs on the other end of the hallway.

Most of the bedrooms were on the first floor, but Rose had turned a large, open, garret room into her private sanctuary. The huge French doors under the eaves of the building opened out onto a balcony, and she'd spent several sleepless nights sitting out there, watching the stars.

The starlight beckoned to her tonight, winking at her through the clouds that were rolling in. She wrapped herself in a warm blanket and opened the glass door, shivering when the wind swirled around her.

Rose rubbed her finger over her wedding band. "Where are you, love?" she murmured.

It had been years since Roes had believed in Santa Claus, but Tony's confident belief that the Doctor would be here tomorrow stuck with her. And really, she'd seen stranger things than a man who travelled around the world delivering toys to every single child.

"Please," she whispered to the stars. "I don't want anything else. Just bring him back to me."

The stars sparkled, and for a long moment, it felt like the world was holding its breath. Then, to Rose's amazement, it started to snow.

She held out her hand and watched the tiny crystalline snowflakes melt into her warm skin. Christmas magic seemed to be in the air.

oOoOo

Martha sighed as she followed the Doctor from the ferry back to the TARDIS. The skyline of Old New York was behind them, with the Empire State Building the tallest building of all. A month of travelling with the Doctor had shown her incredible things—the past, the future, far-off places…

But more than anything, it had shown her how much he still missed Rose.

And after last night, watching him offer himself up to the Daleks not once but twice, Martha had to wonder how much longer he would survive without her. He certainly didn't want to, that much she knew.

"Meant to say, I'm sorry," Martha ventured as they approached the TARDIS.

The Doctor looked back at her as he unlocked the door. "What for?"

She shrugged. "Just because that Dalek got away. I know what that means to you." She'd pieced together enough from his angry ranting to know the Daleks had a part in whatever had taken Rose from him. "Think you'll ever see it again?"

The Doctor smiled bitterly. "Oh, yes. One day."

Martha took a deep breath as she followed him into the TARDIS. All his manic energy was gone, and his eyes were shuttered as he slowly moved around the console, adjusting the dials.

"Can I ask a question?"

He looked up at her, a wry smile on his face. "Martha, in all my years travelling with humans, I've learned it's impossible for you to not ask questions."

She shook her head. "Right, but I mean… Like, a personal question."

Caution flickered in his eyes, but he nodded. "I reserve the right not to answer though," he warned.

The arms crossed over his chest weren't encouraging, but Martha refused to back down. He needed help, even if he didn't want to admit it. And she had a feeling there was only one cure for his depression.

"Have you looked for a way to bring Rose home?"

The Doctor stumbled back, accidentally shifting the dematerialisation lever in the process. "Of course I have!" he said as the time rotor slowly moved, taking the ship into the Vortex. "I spent six months trying to find a way to bring her home. It isn't possible."

Martha tilted her head. "You're brilliant though," she persisted. "Surely there's some kind of way…"

The Doctor shoved his hand through his hair. Martha's words brought back all the inadequacy he'd felt when said goodbye to Rose on Bad Wolf Bay. She'd expected him to come take her home, and he'd let her down.

He took a breath. "Rose is trapped in a parallel world," he explained. "There are billions of worlds out there, with other versions of Martha maybe leading slightly different lives." He looked at her soberly. "Travel between parallel universes is impossible, or should be. Too much going back and forth and you fracture the walls of reality."

"So you're saying you could bring Rose home, but…"

"But two worlds would collapse in the process," he finished.

"Blimey." Martha blew out a breath.

Despite himself, the Doctor laughed. "Exactly."

The TARDIS shifted fully into the Vortex, and the time rotor stopped moving. In the sudden stillness of the console room, the Doctor heard a distinct, and yet impossible, sound.

There was something tapping on the roof of the TARDIS.

"What is that?" Martha whispered.

The Doctor cocked his head, trying to listen. Over the hum of the TARDIS, he could hear a musical jingle, almost like… Sleigh bells?

"We're in the Vortex," he told Martha quietly. "There's nothing out there. There can't be."

Two sharp raps at the door immediately followed his words.

"Then what's that?" Martha asked.

The Doctor stared at the door for a long moment before walking slowly down the ramp. He was one hundred percent positive that they were in the Vortex. It felt different here than anywhere else in the universe. And it shouldn't be possible for anyone to knock on their door.

Well, there were creatures that lived in the Vortex, but they weren't really the type to knock. They were more likely to chew their way through hull casings and come in uninvited.

The mysterious person knocked three more times, and then, to the Doctor's astonishment, a voice called out to him. "Open the door, Doctor. I have a present for you." Despite himself, the Doctor's curiosity got the better of him and he threw the door open.

Whatever he'd expected to find on the other side, it was not a floating sleigh pulled by eight tiny reindeer. The man sitting in the sleigh was unmistakable, from the tip of his fur-trimmed red hat to the toes of his black polished boots.

"What?" the Doctor gasped.

"Santa?" Martha exclaimed.

Santa Claus tapped his nose and winked at them. "Well, there you are, Doctor! I was starting to think you didn't want the present I have for you."

The Doctor leaned against the railing. "What present would that be?"

Santa hopped out of his sleigh into the TARDIS, his movements as lively and quick as his legend proclaimed. He held a piece of vellum in his hand, and the Doctor could just make out the word, "Nice," written across the top of the list in flowing script.

Santa perched a pair of wire-rimmed glasses on his nose. "I've been getting letters from a very eager boy named Tony Tyler. It seems he wants to meet you for Christmas."

The Doctor's hands shook. "Tyler…?"

Santa's eyes twinkled at him over his glasses. "Tyler," he confirmed. "Your brother-in-law."

The Doctor sagged as a fear he had never acknowledged was banished. Rose hadn't been pregnant. There'd been something in her denial that had made him wonder—her hesitation, maybe? The little laugh as she said no? But now he knew it really had been Jackie.

Then the rest of what Santa had said sank in. "Rose's little brother asked to meet me for Christmas?"

Santa rolled his list back up and returned it to a pocket in the lining of his cloak. "Oh yes, he's been most insistent. And just tonight, his sister put in a request of her own."

"Hang on." Martha spoke up when the Doctor tried to process this. "How do you know all of this?" she demanded. "And how can you possibly be able to take the Doctor to his wife? At least, I assume that's what you're offering."

"Ho, ho, ho!" Santa chuckled, and while his belly didn't shake like a bowl full of jelly, the sound did warm the entire room. "Martha Jones. Ever the sceptic, even when you were a child. Surely a month of travelling with the Doctor has taught you that there are some things outside your scope of understanding?"

The Doctor shook his head. "Martha's right though. Rose is trapped in a parallel world. There's no way to bring her home or go to visit her."

He narrowed his eyes, and Santa rocked back on his heels as if to say, "Go on."

"But if that's true, how do you know Tony? How did his Christmas wish reach you?"

"And now you're finally asking the right questions." Santa beamed at them, then moved past the Doctor to the TARDIS console. "Time Lords were not the only pan-dimensional beings in the universe, Doctor," he said as he pulled something out of his bag. He bent over the navigation panel of the console. "How else do you think I could get to every single house on Earth and leave toys for the children on one night?"

The Doctor tugged at his ear. "Wellllll…"

Santa looked back at him over his shoulder. "You thought I was just a story. I'm not, though, as you can see."

"I'm still not certain I didn't actually get shot by that Dalek, actually," the Doctor retorted.

The TARDIS chimed, and the Doctor's eyes widened. Santa nodded and gestured for him to come forward. "Your ship knows who I am, Doctor. And she's let me give her a tiny modification."

He pointed at a new button on the console. "One press of that button, and the parallel universes will be open to you." He winked at him. "I took the liberty of setting it to sync with one particular universe. I hope you don't mind."

oOoOo

The Doctor and Martha stared at each other for several moments after Santa left. "Well, are you going to push it?" Martha finally asked, pointing to the red button on the console that the jolly old elf had said would take them through the Void.

The Doctor stared at it. "Do you think I should?"

Martha rolled her eyes. "I thought you were looking for a way to find Rose," she pointed out.

"I was! I am," he corrected. "But… this seems a bit too good to be true, doesn't it?"

Martha shrugged. "I think you need to try at least," she told him. "What if it works and you wait weeks to try it? How would you explain those weeks to Rose?"

The Doctor swallowed hard. Martha was right. He just didn't know how to handle having his dreams literally handed to him.

He reached for the button, then pulled back. "I'm taking you home first," he said decisively. Martha opened her mouth, but he shook his head quickly. "Travel through the Void is dangerous, and we don't even know if this button will work. What if it's a trap? Like the portkey in Harry Potter."

"Then you shouldn't go alone," Martha argued.

But the Doctor refused to budge, and twenty minutes later, he was dropping Martha off in London with a promise to pick her back up after he'd found Rose.

Alone in the console room, he shoved aside the fears that still lurked in his mind. Whether it worked or not, he had to try.

As soon as he pushed the button, he knew it had worked. The TARDIS lurched and shrieked unhappily as she moved out of the Vortex and into the Void. For half a moment, the Doctor worried that the Void itself would kill her, as it had nearly done the last time they'd taken this trip.

But Santa had been true to his word, and the stabilisers he'd added soon kicked in. The Doctor laughed and grabbed onto the console. It was Christmas, and he was finally going to see Rose again.