There came a sound from behind them.The Doctor turned, thinking that Margwyn was still alive.

Gandar, still hanging from the sword through his chest, was shakily aimingh is staser in their direction.

‘– live,’ finished the Doctor, his eyes widening in shock.

‘For Gallifrey,’ said Gandar. And he fired.

The bolt struck Compassion in the centre of her chest. She was blasted backwards. Over the edge of the parapet. The gun fell from Gandar’s hand and he slumped.

‘Compassion!’ bellowed the Doctor.

He and Fitz flung themselves to the battlements. Compassion’s body fell through the air as if in slow motion, her scream echoing on the wind.

The Doctor and Fitz watched helplessly, their fingers gripping the wall, caught in this nightmare, as she spun towards the ground.

Compassion’s head was filled with the scream. But alongside it was a thought. The staser bolt hadn’t hurt at all. She felt the change roaring up to take her. She asked it if she would die. It told her that the change would make her everything she wanted to be. The bridge over the moat leapt up to kill her. And she gave herself to the change.

The Doctor had told himself that he would not close his eyes. His arrogance had killed her. He should have checked Gandar’s body. Now he’d lost everything again.

He kept looking, helplessly, as Compassion neared the moment of her death.

But then a sound so familiar that it took a moment for him to realise what it was began to resound across the downlands.

The Doctor stared in astonishment.

Was it his eyes failing him, or was Compassion –

Fading in and out of existence. She was about to hit the bridge. She vanished completely.

The Doctor restrained the urge to bellow a relieved laugh at the sky. The consequences of this were too huge. He made his fingers let go of the parapetand turned to meet Fitz’s boggling gaze with a baffled smile of his own.

‘What –’ he began.

The Doctor put a finger to his lips. From across the blackened turret, the sound came again. It started off distantly, something hard to distinguish from the background shudders and tremors that were still shaking the castle. But then it came more bravely and distinctly. The Doctor closed his eyes and luxuriated in it. Could it really be? To him that sound meant home, safety, freedom – And adventures in time and space.

A wind started to whip up the ashes of the blackened tower. It increased with the volume of the noise until something started to form out of thin air at the centre of the vortex.A human figure. The Doctor opened his eyes again and stared.With a wheezing, groaning sound, Compassion appeared.

*

Compassion screamed. She staggered, and would have fallen, except that the Doctor leapt forwardand caught her.

‘Are you. . . Have you. . .' He saw that her face was flickering through thousands of expressions, the muscles twisting into shapes that ranged from joy to terror.

‘The change!’ she gasped. ‘My cells are being replaced by. . . by contours in space-time. I’ve become. . . I am. . . A TARDIS!'

‘The Doctor opened his mouth in horror at hearing that his fears had been confirmed.

‘I’m sorry,’ he said.

She coughed and jerked, her eyes imploring him, looking as if she was drowning. The Doctor felt that he could almost see the new paradigms invading her system, her biodata warping throughout the continuum. The pain in her face was terrible to see. He held on to her hands as her grasp tried to crush them, and made sure that he held her gaze steadily as her pupils shrank into the far distance of her eyes.

Shrank. . . and vanished. For a moment, he held in his arms what he could only take to be a deadbody. But then Compassion gave a jerk, and closed her eyes, and yelled again, and kept on yelling in a low, continuing scream that sounded like a birth.

The scream cut out, and she thrashed even more, and then was still. As if from a long way off, she started whispering, and the Doctor had to incline his head to hear what she was desperately trying to communicate to him.

‘When you altered my receiver to pick up signals only from your TARDIS, you started this process. The Remote are built to absorb information. I was programmed with everything about the TARDIS: its culture, its personality. Finally, its abilities.’

‘Like the chameleon thing, and teleporting across rooms when things aregoing to fall on you,’ said Fitz, kneeling beside them.

Compassion jerked again. 'The block-transfer equations were solving themselves in my nervous system. That was the change that I could feel coming,the one I didn’t want to embrace. You wanted me to be more human. . . But I’ve become something a long way from human.’

Then she opened her eyes again. They were spiralling with the colours of the vortex.

‘I had no idea,’ the Doctor whispered grimly. 'I would never have let this happen. Are you in pain?’

‘Sometimes. And. . . I’m not sure it’s pain, it’s. . . Oh.’ Her eyes flickered for a moment, faster than the Doctor could follow.‘I’ve just found out that I don’t have to feel it like that. Just as. . . Ah!’ With a jerk of her muscles, she sat up, suddenly in control. ‘Information. That’s better. Woo. That’s. . . that’sa relief!’

And to the Doctor’s amazement, she actually started to laugh. He helped her to her feet, still horrified. ‘Are you. . . ?.'

‘I’m not who I was. And I can’t go back.’ Her head flicked back and forth between the two of them, as if taking on board the idea of seeing something. ‘Everything I am has been replaced by something else, something other, but. . . ’ She took a step away from them, flexing her hands, as if her fingers were twirling through strands of information. ‘I can find all the old pieces of me. Yes, there’s me. There’s what I was. Still got that. But. . . all this!' That wasa sudden shout, of exclamation, of amazement. ‘All this new. . . new. . . ’ She couldn’t find the words, turning to stare at them exultantly.

‘You’re hysterical,’ said the Doctor.

‘All these new emotions. . . ’‘Yes, yes! The big emotions of time and space. I’ll have to learn how to handle them, but, Doctor, do you understand what I can see now? It’s so astonishing. And complicated. And funny. There are all sorts of little built-in ironies and punchlines. It really adores itself, too, the poor thing.’

‘Poor thing?’ asked Fitz, still obviously a couple of steps behind.

‘The cosmos,’ she said, wonder still in her voice. ‘You must let me show it to you. And you to it.’

The Doctor moulded his lips with his fingers into his familiar expression of pondering. ‘So it wasn’t my old Type 40 that those other TARDISes were talking to during the Fendahl affair, it was you! And this explains why the scanner blew up on Skale. And now I understand who I met in the vortex. Your future self, snuggled up in the dreams of Constantine. The only way his unconscious could make sense of you was as a goddess being born, so in his dreamscape he created Brigida, the power source for those who followed her. What a tangle of purposes.’

Compassion was about to reply with a laugh, a scream, another big statement. But suddenly, from all around them, there came a blaze of noise. It was the same sound that Compassion had made on her arrival, the rending of space-time by powerful engines. But this time it was much faster, and it came from every corner of the castle.

The Doctor spun round. The castle had developed hundreds of new towers, and from each one were emerging Chancellery Guards in their red and white uniforms, sprinting towards them with weapons drawn. Then the noise was all around them.

And suddenly the top of their tower was indoors.

Compassion hiccuped. ‘Oops. Sorry. TARDISes inside other TARDISes.’

They were inside a meticulously decorated drawing room in the style of an English country house in the 1920s. Arranged across the marble floor from the Doctor and his companions was a chaise longue, with a Chancellery Guard standing to attention on either side of it. And arranged on that chaise longue, in a long green gown with her pearlsand an opal-jewelled headband across her brow, lay –

‘Madam President,’ said the Doctor. ‘Romana.'

*

‘Doctor,’ the lady President nodded to him. ‘Mr Kreiner.’

And then she smiledbroadly at the sight of Compassion. ‘Type 102.’

The Doctor stepped between them. ‘Her name is Compassion. And you’ve regenerated. You look like my mother. How worrying.’

Romana sighed in irritation and slid to her feet. ‘And you. Doctor, look like a barbarian. Do put a shirt on. No, names are quite inappropriate for whatyour friend has become. She’s –’

‘The mother of your next generation of living TARDIS capsules.’ the Doctor finished grimly. ‘The type 103s. I’ve met one, and even she had a name. You think they’ll give you the edge in the war that’s coming.’

‘We know they will. Your little jaunt into the Obverse, when Compassion’s true potential began to be realised, tipped us off. Doctor. You set off such a disturbance there, set in train events that we really couldn’t help but monitor. We saw so many shadows of the future forming in the blue, so manypotentialities. . . ’

‘Iris tried to turn me away from there!’ The Doctor clenched his fists, cursing his fate.

‘She was too late.’

He took a step towards Romana, his eyes interrogating her, unable to believe that this was what had become of his former friend. ‘And that’s why Cavis and Gandar were sent here,’ he muttered through clenched teeth. He could still see the bodies arranged around the room. Gandar hanging obscenely from that sword among the coat hooks. ‘To start this entire conflict, to convince the dream of Constantine that they were on his side, because he was one of the few entities in the universe power-ful enough to trigger her final transformation, but weak enough for them tocontrol!’

‘The pieces did all fit together with a sense of historical inevitability, but we were wrong about the amount of encouragement your friend needed.’ Romana smiled. ‘I think the young lady rather wanted to be a TARDIS all along, though she didn’t know it.’ She turned to Compassion and cooed at heras if she was a kitten. ‘Didn’t you?’

The Chancellery Guards from the other TARDISes burst in through everydoorway and surrounded them.

‘So what happens to me now?’ asked Compassion, stepping past the Doctor to face Romana.

The President reached out to touch her new prize, holding her fingers an inch away from Compassion’s hair as if awed by her existence. ‘You’re our property, now. We’ll take you back to Gallifrey, and mate you with another capsule. I’m sorry, I really am. I’m aware the process won’t be pleasant, but none of us have any option. Don’t think of dematerialising. This TARDIS is ready for you to try it. You’d only hurt yourself.’

‘I won’t let you do this!’ shouted the Doctor.

The guards sprang forward and grabbed hold of him and Fitz, restraining them. He struggled to shout at his former friend once more. ‘What is it about being President that does this to our people, Romana? There was a time when you cared desperately about slavery and injustice!’

‘Please, Doctor, don’t be so boring. I’m simply a servant of history.’

‘Tell me! Tell me how much you knew! Did you know about the methods your agents would use? Have you really changed so much?’

Romana sighed and stepped up to him, reaching out to put a serious hand on his shoulder. ‘I must do my best for the people of Gallifrey. That thought got me through this regeneration with my marbles intact. Perhaps that’s the curseof the Presidency, you see, that you literally become someone for whom that office is everything. It’s so beastly.’ She lowered her head to avoid his gaze. ‘No, I don’t know all the details of what happened here in my name, in pursuit of my plan. But I’m not going to apologise for them, either.’ She wandered over to the chaise longue and toyed with a cushion. ‘When I say that I serve history, perhaps I should rather say that I am its slave. The development of the living time capsules in the future is a fact. It happens! We know it happens!’ She turned back to the Doctor, almost pleading with him. ‘Even you wouldn’tbe so terribly foolish as to try to fight the destiny of the universe.’

‘The destiny of Gallifrey, you mean!’ muttered the Doctor. ‘Has it occurred to you that perhaps the Time Lords aren’t going to rule for ever? That perhaps your enemies will win?’

That seemed to sting Romana. ‘Not,’ she snapped, ‘during my term of office.’ She bobbed a glittering nail at Compassion ‘Take her! Let’s finish this!’

Two guards approached, carrying a large piece of scientific apparatus which resembled nothing more than a pair of manacles.

Compassion looked desperately across to the Doctor.

But all he could dowas stare back at her helplessly.

*

‘All right!’ shouted the Doctor. He turned to look into Romana’s mocking green eyes. ‘I may not like what you’re doing, but we Time Lords have to look at the big picture. What’s a single life, what are the thousands of lives given in this war, compared with the safety and security of the entire universe?’

‘Doctor!’ cried Fitz.

But Compassion was nodding.‘I agree. This is the sacrifice I was created to make. This is my destiny. I can see that now. Doctor, Fitz, you should be happy for me.’

‘Just let us say goodbye,’ said the Doctor quickly. ‘Then you can be on you rway and Fitz and I will find somewhere on Earth to settle down.’

Romana gestured to the guards to release them. ‘Are you sure we can’t take you anywhere else?’

The Doctor cradled his chin in his hand for a moment, thinking. ‘Perhaps we could do with a lift. It is my favourite planet, but with Avalon landing there, it’s going to be in a bit of a mess.’

‘Well, I have plenty of TARDISes. I could lend you one to replace the Type40 that got destroyed between dimensions.’

The Doctor beamed. ‘Really? Great!’ He grabbed both Romana’s hands andshook them firmly. ‘It’s a deal! Can I have one of the Type 98s? With the holographic scanner? After all,’ he gestured towards Compassion, who was speaking softly to Fitz, ‘I can offer you a fantastic trade-in.’

Romana laughed. The Doctor wandered over to Compassion and Fitz, and drew them to himin a hug.

As their three heads met, Compassion whispered, ‘she doesn’t know aboutthe amulet, does she?’

‘No!’cried the Doctor loudly, as if reassuring her that everything would be all right.Then he pulled Fitz back from her and took a step back himself, taking a last look before he let her go.

He smiled at the assembled guards, who smiled back at this fine example of a Time Lord doing his duty to Gallifrey.

Then he reached out and fondly touched Compassion on the nose. ‘Dingdong!’ he said.

Compassion spread her arms wide. And then, impossibly, her body folded open into a gaping doorway that was far bigger than Compassion herself. A brilliantly lit tunnel lay beyond.

‘Ow,’ she said. ‘I hope that gets easier.’

The Doctor grabbed Fitz by the collar and threw him through the doorway.Then he leapt for it himself.The doors slammed behind him just in time to deflect a barrage of staserfire.

*

The TARDIS called Compassion sped down the tunnel of the space-time vortex, a determined look in her eye. She held her arms crossed over her chest, her hands made into fists.

Right behind her came dozens of white, spinning capsules, gaining groundevery moment.

The Doctor and Fitz raced along an ornately polished corridor of wood panels, past dignified oil portraits in styles ranging from classical to cubist of the Doctor’s family, friends, and past selves.

‘Very nice!’ shouted the Doctor. ‘But we need to find the console room!’

They skidded round a corner, and found that a banner hung across thehallway in front of them. It said, THISWAY! in big happy letters, with an arrow pointing to the left. In brackets under the arrow, it added, EVENTUALLY.

They raced off again.‘You know,’ Fitz panted, sounding utterly lost and boggled, ‘in the past, whenever I thought about being where we are now, the whole experience wasmuch more pleasurable.’

The Doctor gave him one of his hard stares before bolting off along anothernarrow corridor. They raced past doors labelled AWFUL TRUTHS, HOPES FOR THE FUTURE and THAT DREAM ABOUT FITZ from behind which they heard terrible screams in his voice.

‘She’s got a sense of humour now,’ he said. ‘That’s going to take getting used to. Especially with her being a building.’

‘More than a sense of humour: a sense of being human!’ the Doctor called, leading the way over a narrow bridge that spanned a vast, dark chasm. He’d grabbed a shirt and a frock coat from an obliging clothes line that had beenhanging across one of the corridors, and was tucking himself in as he ran.

He suddenly halted, and put a palm up to stop Fitz as well. ‘Which is even weirder in a building. Look down there,’ he whispered.

In the depths below, nebulous forms swam and flickered with bursts of sudden illumination.

‘I think that’s her unconscious,’ said the Doctor. Beside him, he suddenly found there was a plaque upon which was en-graved, DROP A PENNY, MAKE A WISH.

The Doctor fished in his trouser pockets, found a coin, and threw it into the depths. ‘I wish to find the console room!’ he called after it. ‘Right now!’

He turned back to the bridge, and found that a series of plates had been riveted into the metal, each bearing the inscription CONSOLE ROOM HISTORIC WALK– THE PRETTY WAY.

They sighed and set off again.

‘She’s just showing off now,’ Fitz muttered.

They burst open a pair of huge golden doors on the other side of the bridge and found themselves, to the Doctor’s initial delight, in a forest. But as the path turned into a track, and the light grew dim, he started to realise where they were.

‘We’re beyond the civilised self,’ he whispered. ‘In the places of nature and emotion.’

There came a cry from the distance that sounded like something human. The distant sounds of water, dripping from every branch, washing down through the soil and circulating the ship, were all around them. The darkness only increased ahead.

‘I’m never going to be in control of her,’he said. ‘There’s no certainty here. There’ll always be something here to scareme, over on the dark side of her mind. And perhaps I deserve that, for letting this happen to her. Whatever brave face she puts on it, whatever joy she’s accessed now, she must be absolutely terrified.’

Fitz kept his eyes on the path. ‘Doctor,’ he said. ‘So am I.’

The Doctor just put a hand on his shoulder.

They came to a moss-clad flight of steps, and made their way down them. At the bottom, there was a cave mouth. They went inside. It was dank in here, but there was something about the rock walls that was recognisably TARDIS-like. Pipes and valves led along the seams of the corridor, and every now and then there was the scarred hint of a roundel. The floor became metal after a while, a grille, and the Doctor could seethings moving under it, whispering past.

‘Of course you put the console room here,’ he murmured to the ceiling. 'To remind me of my responsibility. To let me know we’re on the run, that your life’s in my hands.I understand that. Perhaps now I can do what I couldn’t when you were. . . ’ He made himself use the words. ‘When you were human. Perhaps now I’ll be able to look after you, and save you from those who want to hurt you.’

A door smoothly swung open before them. They stepped inside.

It was a dark, forbidding space. Above, the iris of a scanner swung through darkness, sweeping past stars that swam in the night.In the centre, a steely, harsh-angled console stood on a circular platform,surrounded by a metal rail. And below there was liquid darkness, the space into which the roots of the console plunged, drawing life and time up into the machine.

The Doctor and Fitz quietly stepped on to the platform and looked down.

‘So who’s sleeping down there?’ said Fitz.

‘Let’s hope we never find out,’ replied the Doctor, his eyes alighting on the big pair of front entrance doors with shadowy, changing sigils on them.

Compassion, he realised, didn’t know which side she was on, even now. Didn’t know whose insignia to wear.

‘You’ll find something,’ he said, talking with the gentleness he’d use to quiet a frightened horse. ‘Let’s hope it won’t be the Seal of Rassilon.’

Those two hopes echoed from the depths below to the iris above. He could feel her presence in this space. He reached out for the mesh of tiny gears that stood where the coordinate panel should have been, and put a finger on one. When overhead there came a change in the quality of light.

They both looked up.Romana’s ghostly face filled the roof space. ‘You can’t fight history, Doctor,’ she said, quite calmly. ‘We’ll catch up with you. We’ll take back the Type 102 and we’ll have our new race of time capsules. There’s nowhere in the universe you can hide from us.’

The Doctor looked grimly up at her for a moment. He reached for the power-boost control that Compassion had kept from his grasp until she’d been sure of him, until she’d reminded him of his responsibilities.

‘Madam President. . . ’ he said. ‘You can kiss my TARDIS!’

And he pressed the button.

Compassion opened her arms wide to embrace all time and space. She blurred into motion, accelerating faster than the pursuing Gallifreyan capsules could follow. And then, with a trailing echo that sounded like laughter, she was gone into the depths of the vortex.