Dara Morgan shrugged. ‘Stopped you for good? Doubt it, but I’ve certainly slowed you down, so the signal won’t be activated in ten minutes. Probably not for a few days now – plenty of time for the Doctor to stop you.’ Dara Morgan smiled. ‘And my name is Callum Fitzhaugh.’

A deep electronic sigh came from Madam Delphi.

‘Caitlin?’

And the Irish girl, Callum’s beloved who had rejected him nearly ten years before, drew her revolver from her waistband and raised it.

‘Caitlin, don’t,’ Callum yelled. ‘Fight the Mandragora influence. Remember who you really are!’

Caitlin frowned. ‘Cal?’

‘Yes, it’s me!’

Caitlin shrugged. ‘Never liked you then, don’t much like you now.’

And she fired one bullet that went through Callum Fitzhaugh’s brain and out the other side.

He was dead before he hit the carpeted floor.

The newly awoken disciples screamed and yelled in confusion and started to run out of the room.

‘Go with them,’ Donna hissed to the Carnes boys. ‘Get out of here – Lukas, you get Joe home. Don’t stop running till you get there.’ She turned to Wilf. ‘You too.’

‘Blow that, Donna my girl. I’m too old to run and I’m here with you to the end. Told your father I’d look after you, and by God I will.’

It occurred to Donna that the Caitlin woman could have opened fire by now, so she looked to see what she was doing. She had placed the gun on the desktop and now sat facing Madam Delphi’s screens.

The Doctor walked past Donna, almost incidentally easing Netty into Wilf’s arms, muttering, ‘Hold her tight, Wilf. Like your life depends on it.’ He then crouched down beside Caitlin, snaking his hand out for the gun.

‘Take it,’ she said quietly. ‘Callum and I have done enough damage to warrant what I did.’

‘You were under the control of Mandragora,’ the Doctor said. ‘I broke him free of it, he broke you free.’

And Caitlin looked him in the eye, a tear rolling down her cheek. ‘Madam Delphi never controlled me.

Mandragora never controlled me, it didn’t need to.’

‘Then who told you to shoot Dara Morgan or whatever his name was?’ Donna asked.

‘His mind has been… slipping for days. He was beginning to remember things… he was a weak link. I had to eliminate him.’

‘You had to what? Why? He might have just saved the human race! Is that what this has all been about?’

And Caitlin suddenly looked the Doctor straight in the eye. ‘I don’t know,’ she said, a tear starting to well up.

‘What have I become? What has working for this thing done to me? I just killed someone. Oh my God… I just shot him without thinking.’

‘Bit late for tears, chum,’ Donna said. ‘Working with Mandragora, you’ve probably killed loads of people.’

‘I know,’ Caitlin said quietly. ‘I was out of control, hungry for… for power. I wanted control over my life.’

‘I control everything,’ Madam Delphi pulsed back.

‘Including your life!’

‘No you don’t, you stupid box of wires. I chose this life because I thought I wanted it. But you know what, I got it wrong.’ Her fingers were flying over the keyboard now.

‘I’m shutting down the wireless, putting up your firewalls.’

‘That won’t stop me.’

‘No, But it’ll isolate you for a bit.’ Caitlin looked sadly at the Doctor. ‘I’ve done my bit Mr Time Lord. It’s up to you now.’ And she pushed her chair back and knocked into the Doctor. Apologising, she moved around him and walked over to Callum’s dead body. ‘We could’ve had the world,’ she said as she knelt beside him.

The Doctor tried to make sense of Caitlin’s words.

Wireless. Firewalls. Pointless things, Madam Delphi was a far more powerful computer than that. He tapped the keyboard and a blast of purple Mandragora energy nearly took his fingers off. ‘Now now, don’t get grumpy.’

‘I will still destroy you, Doctor. You will be—’ And she fell silent.

Then he saw what Caitlin had really done. She’d talked nonsense, knowing that Madam Delphi would waste a few

subroutines tracking down what she’d claimed to have done. Having found the firewalls and wireless untouched, the computer was now looking elsewhere. It would keep her silent and occupied for… well, not long, frankly.

But there was a calculation going on, he could see it on one of the screens, it was like a mini-virus itself, a self-replicating mathematical equation that was using up bytes with each passing second as, by trying to solve the equation, it actually multiplied it. The Doctor grinned.

Caitlin was good at what she did, even if it would only take Madam Delphi another few seconds to counter it. He glanced towards Callum’s body, expecting to see Caitlin.

The body was alone.

The Doctor felt his pockets. The revolver was still there. But something else wasn’t.

‘Donna,’ he hissed. ‘Donna, I want you to get down to the lobby. All those people will be confused, disorientated.

Half of them might not even speak English for all we know. They need someone cool and rational to sort them out, explain things to them.’

‘But as no one fitting that description is available,’

Donna said, ‘I’ll have to do it.’

The Doctor grinned at her. ‘Oh Donna, you’re the best there is. Now, off you go – no, not you, Wilf. You and Netty stay here.’

‘Why can’t they come with me?’ Donna asked sharply.

‘Family matters,’ the Doctor said. ‘Trust me, they’ll both be downstairs safe and sound with me in a few minutes.’

‘But…’

Wilf stepped up to the plate. ‘Go on, Donna, don’t argue with the man. When’s he ever let you down?’

Donna went.

‘Might not have been the best choice of words, Wilfred.’

‘You ever let her down, Doctor?’

‘Well…’ the Doctor considered. ‘No, actually, but it’s been close once or twice.’

‘Cos if I ever thought you’d let my little girl down, you’d have me to answer to.’

Their eyes met, across the room and, for the tiniest second, a fragment of eternity, the Doctor knew never, ever to let Donna Noble down.

‘I won’t,’ he said. ‘In fact, Wilf, I should say “we”

won’t, cos you’re important right now. To Donna. To me.

To the whole wide world. And most of all, to Henrietta Goodhart.’ He suddenly stood up. ‘Don’t do it, Caitlin.’

Wilf realised the Irish girl was over by a wall, next to a junction box, holding a silver pen. With a blue tip that was glowing. ‘What’s she up to, then?’

‘You don’t know how to use it, Caitlin,’ the Doctor said slowly. ‘And Madam Delphi’s gonna be up and running again in a second. She’ll stop you.’

‘Let her try,’ Caitlin said. ‘And you’re right, I don’t know how to use it, but I reckon if I push this, twist that and shove it all in there…’

‘Cait, no!’

It was too late. As the sonic screwdriver suddenly shrieked with power, too much power, mishandled, used by untrained hands, Caitlin shoved it into the now-exposed junction box, and right into the fibre-optic cables that Johnnie Bates had died linking up only a few days earlier.

There was a flash of purple fire and Caitlin was gone, reduced to atoms along with a chunk of the wall, the cabling and the Doctor’s sonic screwdriver.

‘Right idea,’ the Doctor said mournfully, ‘but there had to be a better way.’

‘That computer’s gone off,’ Wilf said.

The Doctor looked at the screens, and dived down to examine the server. ‘Dead as a doornail,’ he confirmed.

‘We won?’

‘Oh, not at all.’ The Doctor looked at Wilf. ‘I lied to Donna,’ he confessed.

‘I know,’ Wilf said. ‘But you made sure she was safe.

Thank you.’

‘Caitlin cut off the Mandragora energy from the computer. To all intents and purposes, Madam Delphi is gone. Erased. Destroyed.’

‘But that Mandragora energy stuff, it’s still there, isn’t it?’

‘Trapped.’