The Master looked jubilant. 'Rose?' he stared at her a moment, his eyes sweeping over her. 'You're Rose Tyler. The girl in the TARDIS. The TARDIS in the girl.' He turned, shooting the Doctor a triumphant look as he went on. 'The big, Bad Wolf. This…' he said, whirling to face Rose once more. 'This is just too perfect!'

Rose ignored him. 'I asked you a question. What did you do to him?'

The Master glanced over at the Doctor. 'That? Nothing. He's just a little bit older since you last saw him.'

'He doesn't get older,' Rose said, peering over the Master's shoulder at the Doctor, her wide eyes radiating concern.

The Master cocked his head to one side again, smirking once more. 'Oh, you know him very well, don't you, Commander Rose Tyler? One might even go so far as to speculate that you know him... intimately.' Rose shrugged his hands from her arms.

Unperturbed, he went on, 'You're supposed to be trapped in a parallel universe. I heard him,' he jerked his head in the Doctor's direction, 'telling the immortal Captain Harkness all about it. Very moving story,' he mocked. 'I was touched.'

'Yeah,' Rose said, 'touched in the head's more like it. So, you're supposed to be dead and I'm supposed to be trapped on the other side of the void. But you did something stupid. Really, really stupid. You hurt the Doctor-'

'Your precious Doctor-' the Master sneered.

'I. Am. Talking!' Rose snapped. The Doctor's head jerked up, his eyes fastening on Rose. She continued in the same reasonable tone she'd been using previously. 'You hurt the Doctor, but before you did that, you hurt the TARDIS. One or the other and you might've got away with it. Just about. But not both.'

'Which are you here for then? The Time Lord or the TARDIS? Both belong to me now.'

She ignored him. 'And then you decided to kill a tenth of the people on my planet. Just because you could. Because you're the little boy who pulls the wings off flies to see what they'll do.'

'So you're here for what? Vengeance? Don't be silly.'

'I'm here because the TARDIS brought me,' Rose said, her voice quiet. The Master stared at her. 'And I'm here because I learned that names are important. Travellin' with the Doctor, you pick up titles. Hard not to, wanderin' through time and space with a man without a name.' She smiled self-deprecatingly, though it didn't reach her eyes. 'I'm Dame Rose Tyler of the Powell Estate, the Bad Wolf, Commander Tyler. And Defender of the Earth.' She glared at the Master. 'I think that's why I'm here. Because he can't stop you. So I have to.'

The Master was watching her, his head tilted to one side, his hands clasped in front of him. Then he stepped towards her. 'So much potential in you,' he said softly. 'Is that what you saw, Doctor?' he asked, looking over his shoulder. 'Is that why this one mattered so much?' He looked back to Rose. 'You're all over his TARDIS, you know,' he said in a confidential tone. 'Little human girl with a little human life and a little human name scrawled all over the last functioning TARDIS in existence.'

Rose looked up at the Doctor, just for the briefest of moments, before returning her gaze to the Master, defiance in her eyes.

But the Master hadn't missed the flicker of uncertainty. 'Oh yes,' he said, 'you matter to him, Rose Tyler. But not enough. Not nearly enough. He still left you behind. Left you trapped on a parallel world. Replaced you.' Rose kept her eyes on the Master, refusing to look away. 'I wouldn't have done that,' he said, his tone thoughtful.

Rose stared at him, her eyes wide. 'You what?'

'I wouldn't have left you behind,' he said again, taking a step towards her. 'I would never leave you behind, Rose. You're far too interesting. Little commander who can break through the void.'

He was standing very close to Rose now. Martha could feel the tension radiating from the Doctor. Felt the moment he just had to speak.

'Stay away from her,' the Doctor said, his voice quiet. 'You're only doing this to get to me.'

'See?' the Master said to Rose. 'He thinks you're only worthwhile as way to hurt him. Doesn't realise that this has nothing to do with him. Nothing at all.'

Rose stepped back slightly until her back was against the paradox machine. The Master continued his advance.

'Master, please!' the Doctor said, panic evident in his voice now. 'Leave her alone!'

The Master grinned. 'Gives you shivers, doesn't it?' He was standing just in front of Rose now, inches away. 'I can offer you the universe. All that,' he waved a hand airily in the direction of the sky, 'in exchange for so very little. After all,' he added, giving her a shrewd look, 'isn't that what you really came back for?'

'No,' Rose said firmly, glancing around for a way out. 'I don't want the universe.'

'Your planet, then, Defender of the Earth? The lives of the people on your planet?' He cocked his head to the side again. 'Oh I know! I know… what about… the Doctor's life?'

Rose's eyes snapped to his face, studying him intently. 'In exchange for what, exactly?'

The Master stepped forwards again, grinning. Then he reached for her, running his fingers down her cheek. 'I think you know what it is I want,' he said quietly. 'What I'm not afraid to take. What do you say, Rose? The Doctor's life, the life of all the little humans left on your planet… for so very little.'

'Just me, yeah?' Rose scoffed, half a laugh forcing it's way between her lips.

'Just you,' he confirmed. He dipped his head, pressing his lips to hers as his arm slid around her waist.

Beside Martha, Jack tried to move towards them, only to be pulled back by his guard. The Doctor flinched, as though hit.

Lucy Saxon, unnoticed and apparently abandoned, shouted, 'Harry!'

But Rose was already shoving the Master backwards. He smirked. 'You really are fascinating.'

'Yeah, you said.' She wiped her mouth with the back of her hand and looked at Lucy. 'How can you stand it? Definitely a sandwich short of a picnic, this one.' She returned her gaze to the Master, neatly skipping over the Doctor on her way. 'Thing is… I don't need you to save them,' she nodded downwards, contriving to indicate the people on the planet below. 'I can do that myself. And you can't give me the Doctor's life, its not yours to give.'

'I can kill him,' the Master said sharply.

'You won't though, will you? Same reason you won't kill me. He's more fascinating alive. Plus, for all your chat about how I'm interesting and fascinating and whatever, you don't think I'm a threat.' She pushed the Master gently but firmly, forcing him to take another step back. Martha stared, compelled. Why was the lunatic letting her do this? 'Otherwise,' Rose continued, 'you would have called up your little floating-ball mates.'

'You're right,' the Master said. 'Nothing you do can threaten me, Commander Tyler. I could have you locked away like that,' he snapped his fingers.

'Course you could,' Rose said, her tone almost reassuring. 'But,' she said thoughtfully. 'I've still got this.' She bent and retrieved the instrument she'd dropped earlier.

The guards took a step towards her as she aimed it at the Master but he held out a hand. 'I have to admire your bravado, but that,' he said, pointing, 'is still a hairdryer.'

Rose looked at it thoughtfully. Then she looked up, grinning. 'Yeah, you're right. S'useless as a weapon. Never quite got the hang of weapons. But it's really heavy,' she said. Then she raised it over her head, turning towards the open door of the paradox machine.

She looked over her shoulder at the Master, allowing her gaze to briefly flicker over the Doctor this time. Martha saw something akin to pain flicker in her eyes for a moment, before it was replaced with the cocky assurance she'd often seen in Jack's eyes. 'Time Lords,' she said, sounding amused. 'You don't half like to make a big song and dance out of everything. Well, I learned a thing or two from him,' she nodded towards the Doctor, but didn't look up at him. Then she winked at the Master. 'Here come the drums.' She threw the hairdryer into the paradox machine.

Martha watched as it spun through the air towards the console. It was a good throw. A very good throw, she mused as it hit the central console, shattering parts of the machine and sending them flying every which way. The doors slammed shut, as everything around the machine seemed to stretch and convulse at the same time. Jack took advantage of the confusion to grab his guard's gun, knocking the man out in the process.

Rose ran forwards, ducking around the Master and heading for the Doctor and Martha as he pulled her to the ground. She reached them and threw herself down beside them. 'Hello!' she said brightly to Martha.

'Hi,' Martha said weakly.

'What happens now?' Rose asked the Doctor, raising her voice so she could be heard.

'Time's reversing!' he shouted over the din. 'Everything's going back to how it was! How did you know-'

'I didn't!'

'I thought you had a plan!' Martha said.

'Who me?' Rose shouted. 'Nah!' She dug in her pocket and retrieved something, holding it out to the Doctor. 'Here!'

With a shock, Martha recognised the Master's laser screwdriver. 'How did you-'

'Picked his pocket,' Rose said, 'when he was... Well.' She reached into her pocket again, this time withdrawing the sonic and passing it to the Doctor. She looked at him. 'Can it-'

But he was already running the sonic screwdriver over the laser one, grinning to himself when he found what he was looking for, then clicking the laser screwdriver just once, aiming it at himself, and activating it. Martha watched as his hair grew longer, turning dark remarkably quickly. Within a few seconds, the Doctor was restored. He reached out and grabbed Rose's hand, seemingly unable to tear his gaze from her.

'You think you've won?' the Master shouted, holding on to a railing near the machine. 'Think your little girlfriend has upset my plans? Time is reversing, Doctor,' he spat. 'Back to the moment the paradox machine activated. She'll disappear!'

The Doctor stared at Rose and Martha had never seen him look so helpless. Rose stood, pulling her hand out of the Doctor's grip and using the railings to drag herself to her feet. Then she turned, struggling towards the big blue box, one hand sliding under the collar of her t-shirt, dragging a thin chain out. She reached the machine and lifted the chain to the lock, her key glinting in the flashing lights around her.

'Rose, don't! The Doctor shouted, 'it's not safe!'

She looked over her shoulder at him, her expression terrified, before opening the door and slipping inside. Martha stared as the doors slammed closed behind her.

As the room quieted and the wind stopped, the Doctor pulled himself to his feet, extending a hand to Martha to help her up. She took it and got up, staring around the room. 'What happened?'

The Doctor was tucking both screwdrivers away safely in his inside pocket. 'Everything after the moment the paradox machine activated has… un-happened.'

'You!' the Master said, pointing at the Doctor accusingly. 'You and your stupid little human friends!'

Behind them, there was the unmistakable sound of the TARDIS doors opening. The Doctor's head snapped up, his expression unreadable until Rose appeared, stepping out of the TARDIS and smiling at him. He smiled back, his eyes blazing.

'You didn't think she was so stupid when you were kissing her.' The accusation came from behind Jack. Everyone in the room save for the Doctor and Rose turned to look at Lucy Saxon.

'Darling-' the Master began.

'Don't you darling me, Harry!' she snapped. She raised a shaking hand.

Martha nudged the Doctor, who was still holding Rose's gaze. 'Doctor?'

He turned, his eyes lighting on the gun in the Master's wife's hand immediately. 'Now, Lucy,' he began, stepping forward, 'you don't want to-'

'Stay away from me!' she burst out, almost hysterical. 'You're just like him!'

'Yes,' the Master said, gleefully. 'He's exactly like me!'

'No,' Rose said, stepping forwards until she was standing beside the Master, 'no, he's not. It's Lucy, isn't it? Lucy Saxon?'

'Don't you dare speak to me! You little-'

'Careful,' Jack warned, aiming his own gun at Lucy.

'Jack!' the Doctor and Martha burst out at the same time.

'Put it down,' the Doctor ordered. Jack looked at him a moment, then lowered the weapon. 'Now you, Lucy, put it down.'

'The things I did for you!' Lucy said to the Master, ignoring the slowly advancing Doctor. 'And then you kiss her!'

'Darling, it meant nothing. She might as well have property of the Doctor written across her forehead.'

'Don't lie to me, Harry! I know you! You're my husband!'

The Master rolled his eyes. 'This is just too human. Really, I don't have the time for this. Put the gun down, Lucy,' he ordered, his tone filled with bored superiority.

Martha saw the moment Lucy switched targets; saw the Doctor realise it, too. Lucy Saxon fired the gun, aiming it directly at Rose. And suddenly everything happened at once. Jack pushed Lucy to the ground, knocking the handgun out of her grip and pinning her to the deck. The Doctor spun, desperately trying to make it to Rose before the bullet.

And the Master turned where he was, stepping in front of Rose and pushing her to the deck.

Martha stared as the Master fell, blood staining the back of his jacket and making it stick to him. Rose rolled out of his way, but managed to catch him before he hit the deck. Then the Doctor was there, cradling the Master and staring at the other Time Lord with disbelieving eyes.

'Why did you do that?' Rose was asking. 'I could have moved!'

'I have no idea,' the Master admitted. He looked up at the Doctor. 'Its always the women.'

'Why doesn't he regenerate?' Rose asked.

The Doctor sensed her getting to her feet and stepping backwards, away from him and the Master. 'Its just a bullet,' he said to the Master, his voice tight with emotion. 'Regenerate.'

'And what? Spend the rest of my life on this planet? Locked away, poked and prodded by humans?' he laughed, and then coughed violently.

'No,' the Doctor said, aware that he was pleading now. 'You're coming with me. On the TARDIS. I won't leave you here.'

'Look at you, crying for me,' the Master taunted. His gaze switched to Rose suddenly. 'Fascinating. Really.'

The Doctor ignored him. 'Regenerate!'

'I refuse,' the Master said stubbornly. 'I won't spend the rest of my life imprisoned by you! Following you around the universe like I'm one of them!'

'But…' the Doctor said, his voice breaking. 'But its all gone. Gallifrey, the others… Please. There's only us two left now. You can't die.'

Something akin to triumph flickered in the Master's eyes. 'I win.' Then he gasped. 'The drums… Doctor, the drums… will they stop?'

The Doctor stared down at him, watching the light disappear from his eyes. He was aware of nothing else in the room at that moment. He could feel his eyes burning with tears. The Master was dead. The mix of emotions he'd felt since learning Professor Yana's true identity seemed to be crushing him, forcing themselves upon him. Fear at the return of his oldest enemy vying with relief that the face of Boe had been right. That he wasn't alone. Except that now he was. Truly the last of the Time Lords. Alone.

He felt someone take hold of his hands, moving them away from the Master's body and setting it down on the deck gently. Boots he recognised as belonging to Jack approached and the body was lifted away.

Someone was speaking, giving orders. 'Take him into the TARDIS. Keep an eye on him.' The voice was utterly familiar. The voice was Rose. But the tone wasn't, he dimly registered. The tone was Commander Tyler. Whoever she was. The Captain's boots disappeared and the hands that had pulled the Master's body from him gently tugged at his own, urging him to stand. He was aware of the back a blonde head in front of him.

'You lot,' the Master's guards looked up at that, shock the only emotion registering on their faces. 'Keep her somewhere safe. Lock her up until someone can deal with her. I'm sure Captain Harkness'll have something to say about it. He usually does.' The last sentence was delivered in a tone he recognised.

He drew in a deep breath, surprised when it hurt.

Martha appeared at his side, sliding her arm under his, supporting him even though he was perfectly capable of standing.

The blonde head turned and he could see Rose's face. She looked worried. 'Doctor?' he looked up, meeting her eyes. She looked at him a moment, as though trying to read his mind, then turned to Martha. 'Can you take the Doctor inside and send Jack out? I need to get everyone off this thing and I could do with someone who's allowed to give orders in this universe.'

The Doctor felt Martha turning him. He wanted to resist. He should stay here, with Rose. Should see this through to the end. But the Master's body was in the TARDIS. He would have to see to that. No one else to do it now. No one who knew what should be done. The body would have to be burned.

He could see Rose later. When it was over. When he could feel his legs again.