‘So what are you doing here, Zozie?’

Not too original, but – hey, it’s a start.

I smiled. ‘I’m a – collector,’ I said.

‘Is that what you call it?’

‘For want of a name.’

‘And what do you collect?’ she said.

‘Debts outstanding. Promises due.’

She flinched at that, as I knew she would.

‘What do I owe you?’

‘Let’s see,’ I smiled. ‘For assorted workings, glamours, charms, tricks, protection, turning straw into gold, averting bad luck, piping the rats out of Hamelin and generally giving you back your life—’ I saw her begin to protest, but moved on. ‘I think we agreed you’d pay me in kind.’

‘In kind?’ she repeated. ‘I don’t understand.’

In fact, she understood me perfectly. It’s a very old theme, and she knows it well. The price for your heart’s desire is your heart. A life for a life. A world in balance. Stretch a rubber band far enough and at last it snaps back in your face.

Call it karma, physics, chaos theory, but without it, poles tilt; ground shifts; birds drop from the sky, seas turn to blood and before you know it, the world’s at an end.

By rights I could take her life, you know. Today I’m inclined to be generous. Vianne Rocher has two lives – I only need the one. But lives are interchangeable; in this world identities may be passed around like playing-cards; shuffled; reshuffled and redealt. That’s all I’m asking for. Your hand. And you owe me a debt. You said so yourself.

‘So what’s your name?’ said Vianne Rocher.

My real name?

Ye gods, it’s been so long that I’ve almost forgotten. What’s in a name? Wear it like a coat. Turn it, burn it, throw it away and steal another. The name doesn’t matter. Only the debt. And I’m calling it in. Right here, right now.

One small obstacle remains. Her name is Françoise Lavery. Clearly I must have made a mistake somewhere in my calculations; missed something in the general clean-up, because this ghost still won’t leave me alone. She’s in the papers every week – not on the front page, thankfully, but nevertheless I could do without the publicity, and this week, for the first time, the piece suggests foul play as well as simple fraud. There are posters, too, showing her face, on billboards and lamp-posts around the city. Of course I look nothing like her these days. But a combination of bank and surveillance camera footage may yet lead them uncomfortably close, and all it needs then is some random element to be thrown into the mix, and all my elaborate plans are blown.

I need to vanish – and very soon – and (this is where you come in, Vianne), the best way of doing that is to leave Paris for good.