The Doctor went to check on the TARDIS. He needed to know he could get away. He hoped it didn’t still have an electric charge running through it.

He found that the building wasn’t empty after all. There was a young woman sitting on the floor by the TARDIS, where Jess’s body had been. She was idly kicking the toolbox that still lay next to the ship.

‘Hello,’ said the Doctor.

‘Hello,’ said Emma.

The Doctor sat down next to her, crossing his legs.

‘I’m glad you’re not dead,’ he said. ‘I thought you would have left, though. The doors aren’t sealed now.’

‘I left the building,’ she said. ‘But I didn’t have anywhere to go. So I came back to find you. Are you leaving? It’s all sorted now.’

‘Is it?’ The Doctor looked at her. ‘You’ve forgotten the people who died. Not just the ones killed by the Sontarans. The ones from earlier. Laura. Joe. Andy.’

‘But the Sontarans killed them too!’

‘Oh no they didn’t.’ The Doctor shook his head sadly. ‘The Sontarans only arrived tonight. That was pretty clear from the way they acted. Anyway, Sontarans don’t tend to electrocute people, despite what we saw in the arena. And talking of things electric, how about the electrician?’ He reached out a booted foot and kicked the toolbox.

‘The who?’

‘The electrician. I wanted to know what Sid was doing, walking around down here late at night. He had to be quite close to hear you scream. No one else heard you. Sid thought I was an electrician. Then there was this toolbox and these special rubber boots. So when I had the chance, I asked him.’

Emma said nothing. She was biting her lip as the Doctor told his tale.

‘Sid had sneaked out and called an electrician. He thought about calling the police, but he was worried because he’d helped to hush up the deaths. If an electrician could find out what was going on, though, then maybe no one else would die. That was his idea. He told the man to sneak in, and then came down to meet him last night. But someone had found him first. I wonder where his body is?’

Emma reached out and took a hammer from the toolbox.

The Doctor plucked it from her hand. ‘I don’t think so,’ he said. ‘You see, there’s still one more death we have to talk about.’ He looked into her eyes. ‘The death of a young swimmer called Emma.’

The girl took a deep breath. ‘How long have you known?’

‘Oh, I’ve suspected it for a while. You gave yourself away – no big mistakes, but it was enough. You said you’d never seen the bodies, then you talked about seeing Laura floating in the pool. It was pretty clear you were up to something dodgy. It could have been anything, though.’

The Doctor sighed. ‘But there was more. Lots more. The hand I found by the pool. The length of time you were able to stay underwater. I remembered how you’d asked about the Rutans. That threw me for a moment. But you just wanted to find out how much I knew. And I told you.’

He was still staring into her eyes. ‘Except there were a few things I didn’t mention at the time. Like how Rutans don’t like heat – even heated swimming pools. And the big one. How they can absorb electricity, and use it to kill.’

Emma was hanging on his every word.

‘And when I found out the Sontarans were looking for a shape-changer, that clinched it.’ The Doctor looked at her sadly. ‘You’re the shape-changer. You’re a Rutan.’

Chapter Sixteen

EMMA NODDED SLOWLY.

‘Why?’ said the Doctor. ‘Why come here in the first place? Did you crash-land?’

‘Oh no.’ Emma the Rutan shook her head. ‘I was sent here. You see, the war’s heading this way. We’re going to need Earth soon. But it takes time to form a base on an inhabited planet. Wiping out the natives can be costly, too. Much better to get them to do it for you.’

The Doctor didn’t like what he was hearing. ‘You wanted the humans to wipe themselves out?’

‘That was the plan. The Globe Games are a world event. Many of Earth’s nations are on the brink of war. If I was part of the Games, I could push them over that brink.’

‘A scandal here, a murder there?’ asked the Doctor.

‘That sort of thing. So I was sent here to BASE. I could have waited for the Games themselves . . .’

‘. . . but you wanted to practise being human first,’ the Doctor said. He was almost enjoying himself, seeing all the pieces of the puzzle fall into place. ‘As Rutans are used to being in the water, you decided to become a swimmer. You hid at the pool until someone came along on their own. The real Emma. You killed her. Then you took her body apart. You needed to do that to find out how it worked, so you could copy it yourself.’

‘Human bodies are very complex,’ the Rutan agreed. ‘Even when I’d mastered the shape, it took some time to copy the movement. I was found by the human girl Laura. She joined me in the pool, thinking I was Emma. I found out much from her. But she saw I was not swimming in the human way. She knew something was wrong. Then she spotted one of Emma’s hands that I had not disposed of. She began to scream.’

‘So you killed her. Sucked all the electricity out of the building, and zapped her with it. The first power cut.’ The Doctor spoke in a matter-of-fact way, to hide how he was really feeling. ‘Before hiding poor dead Emma’s hand down a grating.’

‘Yes. After that, I was ready. I filled myself with electricity before I tried to swim. That way, I could protect myself if anyone found me.’

‘You didn’t stop at two deaths. Did Laura’s boyfriend suspect something? What about Joe the sprinter?’

‘He was just in the wrong place at the wrong time. Then I saw the electrician poking around as I was on my way to the pool. I knew I would have to get rid of him. It was a close thing, though. I had to wait until he’d taken off his silly boots. I couldn’t shock him while he was wearing those.’ She laughed. ‘Talking of shocks – guess how I felt when your ship appeared!’

The Doctor stood up and turned to face the TARDIS. He hadn’t really looked at it since he’d landed. First there had been the power cut, then it had been electrified.

He walked round to the back of the police box. There was only a small gap between the ship and the wall. It was just big enough to hold the body of the electrician. He had been a short, dark-skinned man with black curly hair and a tiny moustache.

‘I electrified your ship to stop you finding him,’ the Rutan Emma said, joining him. ‘Well, partly that. I would be put to death if I left without completing my mission, and I needed your help. To defeat the Sontarans, I mean. I didn’t think you’d help me wipe out the humans.’ She laughed.

The Doctor didn’t laugh. He wasn’t finding any of this funny.

‘I have a question too,’ she went on.

‘Oh yes?’

‘If you’ve known for so long that I’m not Emma the human, why didn’t you say something before?’

This time the Doctor did laugh. ‘Because I’m a fool!’ he said. ‘I thought you might be trying to change. You were helping me. Oh, I know you just wanted me to defeat the Sontarans for you, but you were still helping. At times, you seemed to show concern for the humans here. Helping Holly when she was hurt, that sort of thing.’

He paused and looked sadly at her. ‘I thought if I treated you kindly, you might realise that my way is better. You might stop the killing. For a moment, I even thought you’d given your life for us all. No human could have survived what happened to you in the arena. Then I realised that you could just absorb the power.’

‘If you’d looked up, you would have seen me in my own body,’ she told him. ‘I hadn’t got a grip on being Emma again. You see, I’d shifted into Sontaran form to get out of the gym. One of them nearly found me when I was talking to you through the cupboard door. Luckily, we shape-changing elite are made to learn Sontaran as a default form.’