The Doomsday Child

A/N: And here we are guys! End of series 3! Thanks for all the continued support thus far, and I have got plenty more coming for this story, just you wait. Things may be a little out of sync due to issues being Timey Wimey but I think you're all gonna love it! So please, review, let me know your thoughts, opinions, and ideas, and the next chapter will be up again soon!

Harry wanted to explore the whole TARDIS immediately. The Doctor believed he would have to physically pull him from the box just to stop him; exploring the TARDIS could take a lifetime if you weren't sure where you were going. The Doctor knew the TARDIS wouldn't let any harm come to the boy, but the Time Lord didn't want his child out of his sight for longer than he had to.

He forgot just how enthusiastic children were. Sure he'd encountered them on his travels, but his own flesh and blood...that was a different story. He'd had children before. He had loved them with both his hearts and felt them break when he lost them, along with grandchildren and the rest of his family. After that moment on Gallifrey in the heart of the war, when he knew what he had to sacrifice, he'd sworn never to have another child. To never take one under his wing, to get attached to one, or to bare his own again. The pain of possibly loosing another was too much to think about. But now he'd broken the promise. But it was the greatest promise he'd broken, the Doctor thought, as he showed Harry more devices on the console.

But the fear was still there. The idea of this small, vulnerable child being hurt. Seeing the Master treat his child the way he did had sparked an anger inside him that could have ripped apart the cosmos. But he'd been unable to act. It stung more, as the pain was inflicted by such an old friend. The Master had known all his other children...maybe it was Harry's human side that had stopped him from seeing the boy as the Doctor's child.

No time to dwell, however. No time to think on memories.

'Please!' Harry begged, as the Doctor took hold of his hand to lead him away from the console. 'Can't we do it now?'

'Do what now?' The Doctor asked.

'Everything!' Harry beamed. The Doctor couldn't help but chuckle. Harry swung on the Time Lord's arm and pleaded again. The bold, brown eyes reminded the Doctor of Rose, which may have allowed him to cave in and let Harry do whatever he wanted. He was going to have to get used to this role again from scratch. With the others...his other children...he'd have given in far too easily and taken them on any adventures he could have, had Gallifrey laws not prohibited it. But now he had all of Time and Space before him. And an eager child who wanted to see it all.

'Let's run the captain back home and find Martha. Then, I promise, you'll be able to see stars forever if you want. Deal?' The Doctor grinned as Harry nodded and raced to the door.

'Hey! Wait for me!' The Doctor cried and charged from the box after the child.

'Jack! Jack!' Harry called as he re-entered the UNIT base. Soldier's jumped out of the way of the excited child, who launched himself at the military dressed captain. 'I saw it! I saw the TARDIS! It's fantastic, just like mum said!'

Captain Jack Harkness grinned down at the child who only just reached his waist.

'What did I tell you kid? You're old man's motor ain't too bad.' The Captain winked.

'Oi! Watch it! Better than that space hopper of yours.' Jack rolled his eyes, but laughed all the same, ruffling Harry's hair. Harry swung on Jack's arm and told him all the things he and the Doctor were going to see. Jack listened intently, but his eyes watched the way the Doctor couldn't stop grinning as the child spoke.

'Bye Osgood!' Harry shouted as they returned to the TARDIS. The scientific intern was pale faced, but waving frantically as the Doctor unlocked the blue doors. The three disappeared from sight, and soon the box began to fade from the UNIT base.

Behind Osgood, a taller woman in high heels appeared.

'You were right to come straight to me.' The woman said as she opened the file in Osgood's hands.

'I just couldn't believe it. And, well, Sullivan wouldn't tell anyone until he'd had a good poke around himself.'

The woman in heels nodded slowly. Her blonde hair falling in her eyes as she studied the security footage of the child. Analysis had been taken, and swabs during the medical. The printed images showed the child to be the spitting image of what UNIT knew to be the Doctor's tenth incarnation.

'Well there's something for the file. My father would never have guessed himself that Time Lords and humans could have children. He will be shocked when I get a hold of him; he's still in Peru.'

'What does this mean?' Osgood asked, her voice rasping.

'Inhaler.' Kate Stewart said without looking up. 'I imagine it means the Doctor is going to be more dangerous than ever. Thank god he's on our side.'

'Pull that one...no next one….one next to that...there we go!' The Doctor grinned as Harry managed to pull on the lever, taking all his strength, allowing the TARDIS time rotor to stop chugging and make the ride less bumpy.

Yet Jack and Martha continued to grip the railings for dear life. The Doctor was more than happy to let Harry pull switches on the console to help fly it – thankfully the Time Lord was fast enough to reverse something if the wrong button was pressed.

The blue box thumped as it landed, and gave another raspy breath.

'Couldn't you wait until we were out before you started to give him driving lessons.' Martha chuckled, as Harry gave her a friendly push. Jack yanked open the door to the TARDIS and breathed deep.

'Never thought I'd say how much I missed Cardiff.' The man laughed as he stepped out. The rest of them followed, and watched as people passed. The events that had occurred would never be known, and the humans of earth went about their business. The four of them moved about the Roald Dahl Plass, each of them not admitting how comforting it was to be silent as they watched the people moved by, untroubled and alive.

'Time was, every single one of these people knew your name. Now they've all forgotten you.' Martha Jones sighed, looking on across the Plass. Harry stood on the railing as he watched people move around. It amazed him just how much had happened, yet hadn't left a mark.

'Good.' The Doctor said. He kept an arm wrapped around Harry's waist as he wobbled on the railing.

'Well, back to work.' Jack sighed. He ducked under the railing.

'Do you have to go?' Harry asked, not wanting the captain to leave. If he could, he'd have all the Torchwood team members in the TARDIS. Even Owen. There was enough room. Jack simply smiled at the boy and ruffled his hair.

'Someone has to keep an eye on this planet whilst you guys are running up there.' Jack nodded his head towards the sky. 'Besides, your Uncle Jack isn't a gatecrasher.'Jack winked.

'I really don't mind, though.' The Doctor smiled softly. 'Come with us.'

'I had plenty of time to think that past year, the year that never was,' Jack turned and glanced at the water feature behind him. Tourists snapping images, unaware of the world beneath their feet, or above their heads. 'and I kept thinking of that team of mine. Like you said, Doctor, responsibility.'

'Defending the Earth. Can't argue with that.' The Doctor smiled. Harry managed to stretch a grin out for the captain.

'Like I said, you'll see me again kid. Gwen would kill me if I didn't let you come visit.'

'Well she is your boss.' Harry grinned. Jack looked taken aback, but failed to rebuke as the Doctor grabbed the Captain's wrist. He began scan the device with the Sonic Screwdriver.

'Hey I need that!'

'Can't have you walking round with a time travelling teleport. You could go anywhere, twice. The second time to apologise.' Once complete, the Doctor allowed Jack to take his arm back. The ex-Time Agent rubbed his wrist ruefully before looking rather pleading towards the Doctor.

'What about me? Can you fix that? Will I ever be able to die?'

The Doctor sighed through his nose. 'Nothing I can do. You're an impossible thing, Jack.'

'Been called that before.' The man chuckled, before standing tall and saluting. 'Sir. Ma'am. Kid.' Jack winked as Harry held his hand up in a salute. The man began his walk away, before quickly spinning on his heel, expressing his concerns of ageing.

'I really don't know.' The Doctor said, as he really was unsure what would become of the captain.

'Okay. Vanity. Sorry. Can't help it. Used to be a poster boy, when I was a kid living on the Boeshame Peninsula. Tiny little place,' Jack reminisced. 'I was the first one ever to be signed up for the Time Agency. They were so proud of me. The Face of Boe, they called me. I'll see you guys.' At this, Jack ran off, unaware of the stunned faces he left behind.

'Face of Boe? As in…?' Harry squeezed his eyes as he tried to remember the story his mother had told him. One with cat nurses and mind control, wasn't it?

'No.' The Doctor said, his face dumbstruck.

'It can't be, though.' Martha gasped. She shared a look with the Doctor.

'No. Definitely not. No. No.' He stressed each 'no' differently as if it would make a difference. But in the end, the two of them laughed at the dawning truth.

'Oh my god.' Martha said. They watched until Jack had long since disappeared via the secret entrance to Torchwood.

'Right. Come on.' The Doctor swung Harry down from the railing, and the boy immediately ran off towards a swarm of birds.

'Be careful! Don't trip!' The Doctor called, feeling his instincts flair up as he and Martha walked at a brisk pace back towards the TARDIS.

'So. You're a dad now.' Martha said, easing into the subject. There hadn't exactly been a lot of time to explore the conversation topic.

'Yeah…' The Doctor scratched his neck absently as he watched Harry chase after the birds before the flew away. '...I will admit, didn't see that one coming.'

Martha chuckled. 'You can say that again. When Leo and his girlfriend announced they were having a baby, my dad gave him a lecture everyday on what needed to be done to look after a child, how to child-proof his flat, and what kind of food to buy.' Martha glanced up and saw the Doctor was gazing into the distance, but she knew him enough to know he was actually listening.

'Child-proof?' The Doctor said quizzically, after a delay. He watched as Harry stumbled momentarily but continued to run around the open space. He made a move to run, but stopped when he saw the boy was fine.

'Yeah. Like baby-gates and making all the electrics safe.'

The Doctor's eyebrows disappeared beneath the spikes of his brown hair as he pondered the safety of the TARDIS. He wouldn't need a gate or something would he? He'd never had a child in the TARDIS before. He'd definitely have to make sure he left the breaks on. And remember to feed Harry. He himself only ate when it occurred to him, but such a young Gallifreyan slash young Human would need regular meals. And a sleep pattern. The Doctor committed all this to memory. Of course, the TARDIS would already know. The ship knew how to look after him, so a child must be easier for the ship.

'You'll be fine.' Martha could almost see the cogs beneath the Time Lord's hair working as he processed this information.

'I really am out of practise.' The Doctor huffed to himself as he placed a key in the lock.

'What?' Martha said, taken aback by the comment. But the Doctor didn't elaborate. He called Harry over, telling him to stop terrorising the pigeons. The boy bound over and ran back inside the TARDIS, Martha following their quick strides.

'Right, London then.' The Doctor pulled the monitor over and began the process of moving the TARDIS. Within a few moments, they landed with another heavy bump.

'Can't wait for you to show him how to parallel park.' Martha laughed as the Doctor made Harry let go of the Matrix adaptor. Martha smiled at the two of them, as the Doctor pointed something out on the monitor screen. He would be alright. She had made her decision, on her travels, alone after Harry surrendered himself. Her family needed her. Now more than ever. She had enjoyed every minute of it, even the moments where he looked right through her. She knew she was attempting to fill a hole she never could. Harry's arrival just proved how much Rose Tyler had meant to the Doctor, and she never could be that. As Harry grasped at the screens contents, Martha turned on her heel and walked down the gangway. The TARDIS door creaked heavily as she stepped outside. She would tell the Doctor of her plans to leave, once she had checked on her family.

Inside the TARDIS, Harry beamed away as he looked at the screen.

'Can we go explore now? I want to find the library Mum talked about. And the observatory. And the pool. And the kitchen!'

'The kitchen?' The Doctor quizzed.

'For when I get hungry.' Harry beamed, and took the opportunity to run down the gangway into the heart of the TARDIS. Hands in his pockets, the Doctor watched as the young boy ran down one corridor, and then then next, and the next, before finding one of many spiralling staircases. He decided to go up, and soon was lost from sight.

'Keep an eye on him.' The Doctor murmured, and the TARDIS seemed to hum in response.

He felt tired. He could go long periods without sleeping or eating but it did eventually catch up on him. As Harry explored, the Doctor decided to go for a change of clothes and to perk his energy up.

Corridors span through the TARDIS like veins in a body. The TARDIS was a living thing, Harry supposed, so maybe they were veins. He climbed stairs that seemed to reach on forever, before deciding to exit onto a random floor. The first room he found was full of chairs. Nothing more. Leather chairs, soft chairs, table chairs, school chairs. Even beanbag chairs.

'How big is this place?' Harry whispered. The TARDIS seemed to like the question, as the walls seemed to hum their response. Soon, a door appeared on his left. As he approached it, the door slid open, revealing the biggest library he'd ever seen. Shelves reached a high ceiling, which was glass and currently showed blue skies, dotted with fluffy clouds. Between the sections were roaring fireplaces, enclosed by comfy sofas and chairs. There were a few books littered on the floor and on chairs, half read, slightly gazed at, and completely forgotten about.

Harry's face seemed stuck in a semi-permanent grin as he dashed from the library in search of the next room. It was the pool. Which he found by falling in. Thankfully, it had been the shallow end. As he gasped air into his lungs, the water drained from the pool, and he found the base to empty. If the TARDIS had a voice, Harry was almost sure it would be tutting at him. As his Nana Jackie did when he played in the rain and tracked mud and water into her clean kitchen.

'Thanks.' Harry said, as he climbed the pool ladders. His sodden clothes left a trail of water through the next corridor. Thankfully, the space ship was not lacking in heat, so he didn't feel the chill, but knew he needed to change his clothes.

'There you are! I thought...why are you soaking wet?' The Doctor enquired, as droplets dripped from the tips of his hair. The Doctor himself had changed out of his brown suit and now wore a blue one.

'I found the pool.' Harry smiled.

'Oh. And I suppose you decided to go for a swim. In your clothes.' The Doctor smiled.

'Maybe…'

'You didn't happen to fall in did you?'

'No…' Harry said, trailed off, trying to walk casually by. But his shoes squelched with every step, and the Doctor refused to suppress his small laugh.

'Just like your mother.' The Doctor mused with a smile. 'She fell in too.'

'She told me you pushed her in!' Harry proclaimed.

'Well...it was more of an accidental nudge?' The Doctor's words drifted off. 'Come on. Best find you something dry. And maybe a room. You're going to need to sleep eventually.'

'I can stay up!' Harry puffed his chest out. 'Mum says I'm allowed to stay up late, you know?'

The Doctor simply cocked an eyebrow, staring the small child down. In turn, Harry turned his face away and murmured something about having a set bedtime. Shaking his head, not absent of smile, the Doctor clasped the small, damp hand in his own and the two wandered the TARDIS corridor. The Doctor knew they were heading in the direction of his vast wardrobe, but it dawned on him he'd never collected anything in a child's size in the way of clothing. He had very few remnants of his own childhood on-board. But the idea of Harry running around in dusty, centuries old Gallifreyan robes seemed slightly absurd.

Thankfully, the TARDIS knew what to do in this situation. They came across a familiar corridor, which made the Doctor's hearts twist in his chest. He knew, that further up this particular corridor, was a door. A door that lead to the room Rose Tyler had occupied. It still held all her things. Her hairbrush, her clothes, bed unmade, and various trinkets from home and away that she enjoyed having. But before they reached that painful reminder, a new door appeared to have sprung up. It slid open, and revealed a cosy room. It carried the coral design from the rest of the TARDIS, and simply held a bed, donned in TARDIS blue sheets, and various other pieces of furniture, such as a desk and large wardrobe. There was even a bathroom attached. The Doctor silently thanked the TARDIS, and proceeded to find a small variety of clothes that would do for Harry.

'Here you go. TARDIS knows best.' The Doctor said with a smile, and began to look around the room the TARDIS had made, Harry going into the bathroom to change.

A large window was besides the bed, and showed a familiar constellation. The constellation of Kasterborous. The twin suns weren't there, but the Doctor recognised those stars anyways.

'Where to next?' Harry piped up from behind. He'd changed from his soaked clothes into simple jeans, red t-shirt with a rocket ship and a grey zip hoodie. The Doctor noticed how he was even wearing the same hi top shoes as himself. His face broke into a grin.

'Let's go see, shall we? I believe Miss Martha Jones will be returning right about now.' The Doctor said. 'What do you think?' He gestured to the room around him, nearly hitting his hand on the coral arches.

'Is this really my room?'

'Yup.' The Doctor popped the P, as Harry smiled.

'I like it. Once I have my things from home here too, it'll be great!' He beamed. The Doctor's smile faltered as he thought. From home. He wasn't even sure how to broach that topic of conversation. He knew no way back to that world...Jack said Harry had fallen through by accident. Like something like that could be a plain and simply accident. And yet, he was here…

'Come on Dad! Race you!' The Doctor was snapped from his thoughts by the name. He loved being called that. In a flash, he left the room and charged up the corridor and down the stairs. Harry was just meters ahead, nearly at the control room.

'Aha! I win!' The Doctor cried as he charged in, scooping the boy up by his waist.

'No fair! You have longer legs that me!' Harry said as the Doctor deposited him on the jump seat.

'Luck of the draw, I'm afraid.' As the two of them had squabbled, they hadn't noticed Martha return. The Doctor's head snapped round as the door finally closed with a click.

'Right then, off we go! The open road!' He began to run round the console madly, pushing buttons and spinning dials. 'There's a burst of starfire right now over the coast of Meta Sigmafolio. Oh, the sky, is like, oil on water.' His hands flapped around his hands in enthusiasm as he spoke. 'Fancy a look? Or back in time? Something educational,' he snapped his fingers in Harry's direction. 'Charles the Second? Henry the Eight. Oh I know! Agatha Christie!' He ran to a stop besides the jump seat. 'I'd love to meet Agatha Christie. I bet she's brilliant.' And just like a switch, the enthusiasm was gone. 'Okay.' Was his last word.

'I just can't.' Martha stretched her words. Harry looked at her, puzzled.

'Yeah.'

'I spend all these years training to be a doctor. Now I've got people to look after.' Martha followed the Doctor round the console, as he seemed to avoid her. She came to a stop besides the seat and placed a hand on Harry's shoulder. 'They saw half the planet slaughtered and they're devastated. I can't leave them.'

'Of course not.' The Doctor bowed his head, but when it rose, he gave Martha a warm grin. 'Thank you.' They closed the space between them and hugged each other tightly. 'Martha Jones you saved the world.'

Looking proud, and with an air of confidence, she nodded in agreement. 'Come on you. You don't get out on giving me a hug goodbye.' She held out her hand, and Harry leapt from the seat to her arms. She crouched down and hugged him tight.

'I'll miss you Martha.' Harry said into her shoulder. Martha smiled ruefully and rubbed his back.

'I'll miss you too. We saved the world, you and me. If that doesn't mean friends for life, I don't know what does.' They pulled apart and smiled. Martha rose back to her full height, and rubbed her hands together uncertainly.

'I spent a lot of time thinking I was second best. But you know what?' Martha said, poking the Doctor in the chest. 'I am good.'

'Yes you are.'

'Are you going to be alright? The both of you?' Martha asked, nodding towards Harry who still held her hand.

'Of course. We will have a right old laugh.'

'You'll have to watch out for him.' Martha said, looking down at Harry. 'He needs someone to keep him out of trouble.'

'I'll do my best.' Harry said, squeezing Martha's hand.

'Ok then.' Martha breathed heavily. She reached up and pecked the Doctor's cheek goodbye, before reached down and doing the same to Harry.

'You look after him. You need him as much as he needs you.' Martha said to the Doctor, who simply gave her a light nod. Martha imitated this before turning and marching from the TARDIS, before she could give herself the chance to change her mind and stay with the two wanderers.

'Oh, and keep this.' She tossed him her mobile, the Doctor only just catching it. 'I'm not having you disappearing forever. If that rings, when it rings, come running. I'll even consider babysitting if you ask nicely.' She said with a smile in her voice. Harry pulled her a face, with Martha could laugh at. 'I'll see you two again, don't you think otherwise, Mister.'

And with that, Martha Jones had the willpower few companions before didn't have; she left the TARDIS, the door closing with a click behind her.

The Doctor sighed heavily though his nose, watching the space where Martha had just been. He may have stood there in silence for an ungodly amount of time, for all he knew. But a small hand slipped into his own and he looked down. Martha needed to leave, to be with her family. But that didn't mean he was alone himself.

He squeezed the small hand, but said nothing.

'We will see her again, right?' Harry asked. The Doctor contemplated that question. He'd been asked that before. And even asked it himself. Many companions he never saw again. But each time one left, he hoped he would.

'Of course.' He squeezed the hand again. The two of them climbed the gangway back towards the console.

'So…' Harry chewed his lips. 'What do we do now?' The Doctor though about this as he pulled a lever on the console down, allowing them to drift in space.

'Wherever you'd like to go.' The Doctor said with a quaint smile. Harry stepped up to the console, scrunched up is face, before picking a button. He pressed the round, orange button in, as as soon as he hand, the echoing horn of a ship could be heard.

The two of them spun round, the Doctor grabbing Harry by the shoulders and flinging them both to the ground as the walls of the TARDIS were pierced by a ships hull. Outside, a bell began to toll.

'What?!' The Doctor coughed though dust and debris.

'I didn't mean for that to happen!' Harry cried out. He scrambled to his feet, where a life-preserver sat. He flipped the white, rubbery ring over to reveal the ship's name printed in black ink. Titanic.

'What?!'