Anji walked alone through the city of tigers. It was a fast walk, a bad walk, shouldering and dodging crowd. Sunlight splashing off concrete and glass, bright faces and clothes.

And on every corner, from every doorway, in every window, the music. Coming down from bedrooms, spilling out of cars and cafés, thumping and shrilling, twinkling and twanging. Opera and bossa nova, zydeco and disco, one tune crashing into another as Anji pushed and pulled her way down the street.

KARL: I think God's favourite colour must be orange.

Anji closed her eyes for a moment. He was a fake. He looked and sounded like a man, a human male with white skin, a long, strong-jawed face and large, pale eyes. But if you touched his skin, if you held his wrist, he was the wrong temperature, he had the wrong pulse. He didn’t even have a name. She called the alien ‘Doctor’ because she didn’t know what else to call it.

And Anji realised: he wasn't possessed, he wasn't transformed. He was, at last, absolutely himself.

Fitz was sitting on a grassy slope just outside the city, with a view of the sparkling lake, playing his guitar.

When Karl was close enough to make out the melody, he stopped to listen. Fitz nodded at him, but didn’t stop playing. Six notes that rose and fell in a pulsing curve.

Sail on, sailor, sail on,

Still listening for your siren song;

Tomorrow is your only home...

The voice trailed off, the hands kept playing for a few more bars, rounding out the chorus. ‘I never could come up with a last line for that bit... I suppose it’s kind of fitting, in a way. That it’s not finished.’

‘Why is that?’ said Karl softly.

‘It’s about him. I wrote it about him a long time back now, before... before we met Anji. Maybe one of these days I’ll play it for him again.’

‘I can’t play your music any more, Karl,’ murmured the Doctor. ‘I don’t forgive you, I understand you. I know the ferocity it took to throw open those floodgates and drown your enemies. But my passion is for something different. Not for vengeance.’ He ran his fingers through the grass, through the soil and flowers and ants. ‘For life. Inexorable, relentless, dogged life.’

He threw his head back and looked at the sky, at the clouds sailing the high breezes above the city of tigers. ‘I’ve already played my concerto.’