‘Nonsense. I know the bottom limit of cold now and will not cross it again. We are very close, my love.’ Jane lowered the cloth and folded it neatly into a square. ‘Mathieu are you willing to . . . hazard another attempt?’

‘Yes, madam.’ He stood from the stool upon which he had been resting and went to his place by the furnace with remarkable steadiness.

‘Jane, I cannot ask you to risk yourself in this way.’

‘You are not asking, I am choosing.’ Jane put her hands on her hips and spread her legs wide in a man’s stance. ‘We have work to do, and I want to see the results through.’

Vincent paused a moment and then shook his head. ‘All I ask is that you not tell your mother.’

Jane could well imagine her mother’s reaction. ‘I would not dream of it.’

They began again and, attention focused by the previous events, found that their next effort produced a sample which they thought might serve. As soon as it was free from the pole, Vincent took a fold of glamour and passed it into the glass ball.

With her vision extended into the ether, Jane watched the glamour fold and then fragment. The pattern, simple though it was, had too many small errors in it to produce the red cone. But the beginning of the path showed promise.

Vincent sighed. ‘Well, that is hopeful at any rate. The theory is sound, but the practice will take some doing.’

Mathieu narrowed his eyes, staring at the ball. ‘May I make a suggestion?’

‘Of course.’ Jane’s own head was worn out from trying to solve this riddle, and she was only too happy to hear someone else’s thoughts.

‘This cone . . . I have been watching as you worked, and I think the pattern goes off because the glass expands as I blow. What if you made a sphere instead of a cone, so the shapes match?’

‘That’ – Vincent rubbed his hands together – ‘is a very good idea.’

‘What about the Sphère Obscurcie?’ Reinvigorated, Jane wondered how they had not thought of it before. Rather than start with beginning exercises, they should have sought folds that matched the medium. ‘It is a single fold, and designed to expand in a bubble.’

Nodding, Vincent took his place, rising up on his toes with enthusiasm.

As Mathieu dipped his pole into the crystal and blew the beginning of a sphere, Vincent wrapped the Sphère Obscurcie in the glass, making both it and the end of the pole invisible. He expanded the glamour so it passed over the group, bringing them within its sphere of influence. Jane quickly matched Vincent’s fold, twisting her cold threads around to add more definition to the channel in the glass. She nodded to him that it was complete.

Vincent released his hold on the glamour and Mathieu stepped away from them to remove the sphere from the pole. Jane gasped.