The Doctor tried to brace himself when the image of the beach flickered. He clenched his hands at his sides to keep from reaching for Rose, and a moment later she disappeared, along with the windy beach she'd been standing on.

Pain replaced her soothing presence in his mind as the bond tore for a second time. The Doctor pressed his hands to his temples and moaned, while his knees struggled to keep him on his feet.

He took a few deep breath, then pushed himself upright and dashed around the console. "You made your choice a long time ago, you said," he muttered while twisting dials and turning levers. "You said you were never going to leave me. It's time to keep my promise now. I told you I would always come for you—I'm not leaving you there, Rose."

The TARDIS hummed loudly in protest as he set the transdimensional coordinates. Going through the Void was always a possibility. The only thing that had stopped him were the consequences. But even though she'd put on a brave face and promised him she would find a way home, he'd felt her agony clearly over the bond, and that drove every other thought from his mind. They were meant to be together, and he would make sure that happened.

The Doctor's hand was on the dematerialisation lever when he felt a shift in the air on the TARDIS. He sighed and looked up, ready to ignore whatever his ship had done to distract him.

He didn't expect to see another person standing on the other side of the console.

"What?" he asked, staring dumbly at the veiled woman.

She spun around, and her mouth fell open in a squeak of surprise. "Who are you?"

"But…" The Doctor shook his head, trying to grasp how this woman had ended up in his TARDIS.

"Where am I?" she demanded.

"What?"

Her voice rose to a shout. "What the hell is this place?"

"What? You can't do that. I wasn't…" The Doctor glanced at the console and the time rotor, then back at her. "We're in flight," he exclaimed, his voice rising in pitch on the last word. "That is, that is physically impossible! How did—"

"Tell me where I am," the woman interrupted. "I demand you tell me right now—where am I?"

The glower on her face was almost frightening, and the Doctor rocked back on his heels. "Inside the TARDIS."

"The what?" she asked, turning her head as if to hear better.

"The TARDIS," he repeated.

"The what?" she asked again, her voice louder this time.

"The TARDIS!" The Doctor bent over the controls, trying to figure out how this woman had gotten into the ship. His hearts clenched when he spotted the coordinates he'd just set—if the interloper had been just a few moments later, he would have been on his way through the Void to Rose.

"The what?"

He shook his head and moved away from the navigation panel to the sensors and started a scan. "It's called the TARDIS."

The woman took a deep breath, drawing her shoulders back before she shouted at him. "That's not even a proper word. You're just saying things."

The Doctor massaged his forehead. He already had a horrific headache from the bond tearing, and her shouting wasn't helping. "How did you get in here?" he asked, hoping to get her on her way and back to where she belonged.

She rolled her eyes and sneered at him. "Well, obviously, when you kidnapped me. Who was it? Who's paying you? Is it Nerys?" She looked up at the ceiling and rolled her eyes. "Oh my God, she's finally got me back. This has got Nerys written all over it."

The Doctor rubbed at the back of his neck. "Who the hell is Nerys?"

"Your best friend," she hissed viciously.

"Hold on, wait a minute." The Doctor looked the woman up and down, finally noticing her attire. "What are you dressed like that for?"

"I'm going ten pin bowling." She gestured to her white satin gown. "Why do you think, Dumbo? I was halfway up the aisle!"

The Doctor had to clench his eyes shut to keep tears from spilling over. His own wedding had only been four months before, and while Rose hadn't worn satin, the white dress reminded him of the sundress she'd worn when they'd exchanged their vows on the beach.

His eyes flew open when he realised the woman had just accused him of drugging her. "I haven't done anything!" he denied vehemently.

"I'm having the police on you!" she hollered as she circled the console. "Me and my husband, as soon as he is my husband, we're going to sue the living backside off you!"

The Doctor blocked her out again as he worked with the TARDIS, trying to get her to let him take the ginger bride back where she belonged. Even if he couldn't go after Rose, at least then he wouldn't be reminded of what he'd lost.

A glimmer of a memory, of a moment, teased the edges of his mind. He'd lost so much… why did he feel like he was missing even more?

The sudden realisation that five seconds of silence had passed for the first time since the woman had shown up in the TARDIS jolted him out of his thoughts. His head flew up and he spotted her running for the doors.

"No, wait a minute. Wait a minute. Don't!"

He was too late. She already had the door open, and the Doctor sighed and walked over to join her, looking out at the nebula. Normally, the flickering pinks and yellows and blues would have looked beautiful to him, but today, they just reminded him that earlier, he had been in orbit around a supernova. This nebula was what was left of his last connection to Rose.

"You're in space. Outer space. This is my… space ship," he told her, wincing when the TARDIS objected at the word. He patted the doorframe apologetically. "It's called the TARDIS."

"How am I breathing?" she asked, her voice soft for once.

"The TARDIS is protecting us."

"Who are you?"

And finally they were getting to the important bits. "I'm the Doctor. You?" He looked at the woman, and she slowly turned towards him, her face a mask of shock.

"Donna."

He studied her for a moment, then asked, "Human?"

"Yeah. Is that optional?"

"Well, it is for me," the Doctor mumbled, not feeling the same impish glee he usually did when he told people he was alien.

Donna sighed, and seemed to slump slightly as the air escaped her. "You're an alien."

"Yeah."

They stared out at the nebula a moment longer, then Donna said, "It's freezing with these doors open."

The Doctor rolled his eyes, then slammed the doors shut and ran back to the console. "I don't understand that and I understand everything. This this can't happen!" He spun around and looked back at Donna, waving his hand for emphasis as he spoke. "There is no way a human being can lock itself onto the TARDIS and transport itself inside." He shook his head and reached into the tool belt draped over the console for an ophthalmoscope. "Some sort of subatomic connection?" he muttered as he studied Donna's eyes. "Something in the temporal field? Maybe something pulling you into alignment with the Chronon shell. Maybe something macro mining your DNA within the interior matrix. Maybe a genetic—"

Donna slapped him, and he wheeled back and gaped at her.

"What was that for?" he asked indignantly.

She drew herself up, then bellowed at him. "Get me to the church!"

The Doctor stared at her for a second longer, then tossed the ophthalmoscope down onto the console. He'd been trying to get rid of her since she arrived anyway. "Right! Fine!" he snapped. "I don't want you here anyway! Where is this wedding?"

"Saint Mary's, Hayden Road, Chiswick, London, England, Earth, the Solar System."

The Doctor nodded as she spoke, his hands moving rapidly to set the coordinates. Donna was a puzzle he and Rose would have loved to solve together, but if he couldn't have Rose, he just wanted to be alone.

Donna paused, and when she spoke again a moment later, the accusatory voice was back. "I knew it, acting all innocent. I'm not the first, am I? How many women have you abducted?"

The Doctor looked up and froze when he saw her waving Rose's purple blouse around. It was the same blouse he'd wept into the day he lost Rose. He felt himself trembling and he tried to look away from it, but he couldn't.

His throat closed up, and he had to swallow twice before he could say, "That's my wife's."

"Where is she, then?" Donna demanded. The hand still holding Rose's shirt went to her hip. "Popped out for a space walk?"

The Doctor grabbed the console, picturing Rose on the beach where he'd left her less than ten minutes ago. "She's gone," he answered curtly.

Donna rolled her eyes. "Gone where?"

The Doctor leaned on the console and closed his eyes, getting the tears under control. "I lost her," he mumbled, without looking at Donna.

"Well, you can hurry up and lose me!" she snapped.

The Doctor sucked in a breath and pressed his hands to his eyes. He could see it again, Rose slipping from the lever and falling towards the Void. Pete catching her, and the last look of love she'd given him before she'd disappeared.

The silence apparently got through to Donna, because her next words were much less strident. "How do you mean, lost?"

The Doctor opened his eyes, aware that his eyelashes were wet. Donna put her hand to her mouth and set the shirt down.

"I'm sorry, Doctor."

The empty space in the Doctor's mind cried out for Rose. She was supposed to be here with him—she'd promised him forever. He could feel the pull of the Void again as he remembered the hope on Rose's face when she'd first seen his projection. She'd thought he was bringing her home, but instead…

He ground his teeth together so hard that his jaw hurt. "Right, Chiswick!" He flipped the lever and sent them hurtling towards Earth—towards Earth, and away from Rose.

It soon became clear the day wouldn't be as simple as just dropping Donna off and going back to the Vortex where he could grieve on his own. The Doctor grumbled under his breath as he chased the robot Santa who had kidnapped Donna down the motorway, but he had to admit the TARDIS' distraction was helping.

Until Donna looked at him and asked if Rose had trusted him. Of course Rose trusted him. She'd had enough faith in him to think he'd found a way to bring her home even though he'd told her more than once that travel across the Void was impossible.

So why had he felt a glimmer of deception over the bond during their last conversation?

The Doctor shook off the realisation as soon as it struck and focused on getting Donna into the TARDIS. The sense that Rose hadn't been wholly honest probably just meant that she'd been trying to put a brave face on their bleak situation.

Still, the sense that there was something he was missing niggled at him all day. He let one corner of his mind work at that problem while he devoted most of his attention to saving the planet one more time. But he still hadn't figured it out when everything was resolved and he could take Donna home.

It was a bit awkward, standing with her in the street outside her parents' home. This was when he would normally invite his new friend to travel with him, but today, he was desperate to be left alone to grieve.

He pulled out the sonic and scanned her quickly. "All the huon particles are gone," he told Donna when the results came back clean. "So I think I'll be off."

Donna looked over her shoulder where they could see her parents hugging through the front window. "Yeah, I'd better get inside. They'll be worried."

The Doctor smiled. "Best Christmas present they could have."

But instead of turning around and going into the house, Donna tilted her head and studied him. "Tell you what," she said after a moment. "Christmas dinner."

Christmas dinner, with family and crackers and the funny hats… He remembered the way Rose had smiled at him when he'd entered the flat, how they'd all laughed together when they'd put on their paper crowns… He shook his head quickly. He wasn't ready for those memories.

Donna must have seen his answer on his face, because she nodded towards the house, an inviting smile on her face. "Oh, come on."

"I don't do that sort of thing," he said, as firmly as possible.

"You did it last year," Donna pointed out. "You said so. And you might as well, because Mum always cooks enough for twenty."

The Doctor remembered the meal Jackie had managed to pull together with less than twenty-four hours notice, and he wondered what the Tylers would do for Christmas in Pete's World. "Donna I just—I can't," he said, his voice breaking a little. "The last time I celebrated Christmas, I was with Rose and I can't. Not without her."

"Rose." Her eyes lit with comprehension. "Is that your wife's name?"

He swallowed hard and nodded. A cold wind blew down the street, and when Donna brushed her hair out of her face, the Doctor remembered Rose doing the same thing on Bad Wolf Bay.

"Where is she, Doctor?" Donna asked, her voice softer than he'd ever heard it. "You said she's safe and alive, but why can't you bring her home? You obviously miss her."

The Doctor shoved his hands into his pockets. "She's trapped in a parallel world," he said, his voice raspy. "And I can't get there. If I tried, two universes would collapse."

As he explained the situation to Donna, he remembered the look on Rose's face when he told her the same thing. She'd been so desperately hopeful when she'd asked if he could come through properly, and he'd known exactly what she was thinking—it didn't matter which universe they were in, as long as they were together. The bleak look in her eyes, the way she'd brushed her hand over her belly as she waited for his answer…

The Doctor froze. The feeling he'd had all day that Rose had kept something from him suddenly fell into place.

"No!" He staggered back until he was leaning against the TARDIS and shoved his hands into his hair. His fingers grabbed and pulled at his hair as he tried to convince himself he was wrong.

Instead, he remembered the determined set of her jaw when she'd said, "Mum, Dad, Mickey, and the baby." The way her chin had wobbled a moment later when he'd tried to ask if she were pregnant. The patently fake smile she'd given him in response.

He slid down until he was crouched in front of the TARDIS, his elbows resting on his knees and his hands supporting his head as a band tightened around his chest, making it difficult to breathe. Rose was pregnant. In a parallel universe, without him. He'd left her to fumble through an inter-species pregnancy alone, and he would never see his child.

"Doctor?"

He flailed when a hand touched his shoulder, and when he looked up, Donna was standing a few feet away from him.

"What's happened, Doctor? What's wrong?"

He scrubbed viciously at his face, wiping away tears. Then he jumped to his feet and shot her a manic grin. A plan was already forming—he would go through and get Rose.

"You're right, Donna. I should go get her."

Donna blinked. "But you said two universes would collapse."

The Doctor waved his finger at her. "Nah, 'cause I'm brilliant. I can go get her." He sighed when Donna raised an eyebrow. "Rose is pregnant," he explained curtly. "I am not abandoning my pregnant wife to a parallel universe—I don't care what the consequences are."

She crossed her arms over her chest. "And I suppose you think destroying the universe is going to win you Father of the Year?"

Her acerbic voice cut through the madness the Doctor could feel threatening at the edges of his mind. What good would it do to bring Rose home, only to have the universe shatter around them?

He looked at Donna, his eyes burning with unshed tears. "I can't just leave them there," he croaked. "I can't."

She pursed her lips. "Of course you can't. But you need to find someone, Doctor. Someone as clever as you who can help you find a way to make it work. And…" She only hesitated a moment before ploughing on. "Someone to stop you. Because right now, you're one bad dream away from breaking all the rules to bring them home."

"Yeah," the Doctor sighed. There wasn't anyone as clever as he was—he would have to find a way to get Rose back on his own. He tugged on his ear and finally gave her a weak smile. "Thanks, Donna."

Her compassionate smile nearly broke him. Desperate to leave before he cried in front of her, he pushed open the TARDIS door and stepped inside. Donna called his name just before he closed the door, and he looked back at her.

"When you get them back, bring Rose 'round for a visit so I can meet her."

Tears swam in Doctor's eyes, and he blinked rapidly. "Yeah. Of course," he promised.

But once he closed the door behind him and took the TARDIS back into the Vortex, every thought left his mind, save one: he had to find a way to bring them home.