‘You actually sound like the Doctor.’ Ace gave her a mirthless smile. ‘Look, I was 16 when I joined the Doctor. “No Nitro-9, Ace,” he told me. Sixteen … and he leaves me to fight off a squad of Cybermen with nothing but a handful of gold coins and a catapult. But when he was in danger, he was the first to use my home-made explosives.’

‘No way,’ said Yaz.

‘The Doctor is more than happy to use weapons of mass destruction when it suits him …’ She corrected herself: ‘Her. She just likes the moral high ground of getting someone else to carry them on her behalf.’

Yaz shook her head. ‘I don’t believe that. She despises violence …’

‘Until it’s necessary!’ Ace leaned forward. ‘Has she ever told you about some of the things she’s done? She tricked the Cybermen into destroying their entire space fleet; hundreds of spacecraft, thousands of Cybermen, wiped out. She destroyed the Daleks’ home planet Skaro using a weapon she helped to design, just to stop them using it themselves. An entire planet and everyone on it!’

‘An entire planet?’ Yaz sounded less certain now. ‘I thought that destroying one Dalek using a microwave was pretty bad …’

‘Ha! So what was that you were saying about improvised devices? And I bet she wasn’t the one who had the microwave …’

‘No.’ Yaz shook her head sadly. ‘It was Ryan’s dad.’

‘You see!’ cried Ace. ‘It’s always the same. I didn’t see it at first, but gradually …’

‘Is that why you left?’ asked Yaz.

Ace nodded. ‘We were escaping from a tricky situation. The Doctor used me. People died.’

‘People?’

‘Well, aliens. They looked sort of like horses … but they were still people.’ She closed her eyes, remembering the horror of the moment.

‘Dorothy …’

The sound of a woman’s voice calling her name made her start. She looked around in surprise, trying to locate the source of the voice.

Yaz looked at her curiously. ‘Are you all right?’

‘Didn’t you hear that?’

‘Hear what?

Before Ace could reply, the call came again, echoing from the stairwell, distant, but urgent. ‘Dorothy …’

Ace got up from her seat and began to make her way towards the door. The voice called her name again, sharper now, angrier.

‘Dorothy! Answer me!’

Dorothy stopped dead, the blood draining from her face. The voice was unmistakable. The same disapproving tone she remembered from her childhood. It was the voice of her mother.

‘Are you OK?’ Yaz was getting concerned now.

Dorothy just stared at her. What could she say? That she thought that her mother was here? Her estranged mother.

Her dead estranged mother.

Shock turning to anger, Dorothy turned and strode towards the voice. If someone was playing games with her then they were going to regret it.