As they watched, a thin film of blue light danced over Olympe’s skin, and gently the feather began to rise until it lay nestled in her palm. She let it rise again.

Al let out a low whistle. ‘Call the Spanish Inquisition, she’s a witch.’

Olympe looked at him warily, mistrust shining in her eyes. ‘I’m not a witch. I don’t think I’m a witch.’ She looked at Ada.

Ada waved Al away. ‘It’s not magic. I told you, it’s science. I think.’

She had gathered them for a better demonstration of Olympe’s powers. Camille had pounced on her as soon as she’d woken up, demanding she use her scant scientific training for a proper assessment – ‘I want to know exactly what I’m dealing with before I’m dealing with too much of it’ – and Ada couldn’t deny she was excited at the opportunity to take out her notebook and pencil and stack of volumes on electromagnetic research.

‘Electricity,’ replied Olympe. ‘That’s what Docteur Comtois called it.’

‘Exactly. If you rub fur on an amber stone you get the same effect, the feather will rise to it. By the same principle an electrostatic generator uses friction on a glass ball to create an electric charge.’

‘Are you sure you’re speaking French?’ asked Al. ‘Because I have no idea what you’re talking about.’

Guil squatted to observe the feather. Olympe let the blue light die from her fingers and the feather drifted slowly down again.

‘But you have no glass ball,’ Ada said. ‘You create this charge yourself.’

Olympe nodded.

‘It does seem as though it is some part of your body’s natural abilities,’ said Ada thoughtfully. ‘May I look at your hands? I promise to be careful.’

Olympe considered her for a moment, then tentatively extended her arms so Ada could take her hands in turn, tracing the lines of her palms. Aside from the mottled, death-like colour and their coldness, they seemed natural. Perhaps the pads of her fingers felt somewhat rough. But that was it. It was no trick.

‘What did Comtois tell you about your abilities?’

‘Barely anything. I don’t think he thought I could understand much. He’s arrogant. This might be my power but to his mind he’s the genius who’ll figure it out.’

‘What about your mother, what did she think it was?’

Olympe’s eyes lit up. ‘She wasn’t scared of me, she was proud of me. She told me that everyone has different skills and talents, but that my abilities were a miracle. She also told me I would have to be brave. All the best people were brave. I – I think she would like you all.’

Ada swallowed against her dry throat and let go of Olympe’s hands.

‘Thank you.’

Camille had moved back to sit in the window seat, watching Olympe, her expression unreadable.