‘Speaking of genius.’ M. Chastain bowed to Vincent, ‘I would like to see this Sphère Obscurcie of which you have written. I understand the theory, but not the technique.’

Vincent returned Chastain’s bow, then created the Sphère so quickly that it almost seemed to appear by itself. Because Jane had seen him perform this glamour many times before, she knew that he had taken a fold of glamour and twisted in his hand so the light in the room twined around itself. He then blew the bubble up into gossamer thinness, until it surrounded him and caused him to vanish from sight. She guessed that he performed it so quickly as a means of showing off to his friend. Other forms of masking glamours involved weaving a recreation of the scene minus the elements one wished to hide. Part of the genius of Vincent’s technique was its simplicity and speed.

M. Chastain narrowed his eyes, stepped into the ball, and vanished. A moment later, Jane heard him say, ‘Again?’

Vincent dropped the folds and repeated the glamour, working slowly so that M. Chastain could follow his movements. On the third repetition, the Frenchman nodded. ‘I think I have it.’

He pulled a fold of glamour from the ether and twisted it. Jane winced, seeing that he spun it in the wrong direction, but when she opened her mouth to speak, Vincent caught her eye and gave a tiny shake of his head. The Sphère would be invisible from the exterior but would not let light pass through. She held her tongue as M. Chastain expanded the bubble. In a moment, he harrumphed and popped it. ‘That was unexpected.’

‘Mirrored?’

‘Yes. Most unpleasant to see oneself distorted upside down on a vast silver bubble. What did I do wrong?’

‘Jane?’ Vincent beckoned her to join them.

She hesitated, feeling as though she were intruding on a conversation of two colleagues. ‘You twisted the fold with the clock. It must go widdershins. If you do not twist at all, it is completely dark within.’

‘Fascinating.’ M. Chastain executed the glamour again, to perfection this time. ‘It only hides items which are completely within the Sphère, yes?’

‘Correct.’ Vincent tucked his hands behind his back, in his lecturing posture. ‘I used a gossamer weight of glamour, which flows around objects that intersect it, leaving them visible. Had I used a heavier weight, it would have penetrated those items and shown their interior.’

It was a clever solution, and Jane thought she could be justly proud of her husband for his invention.

‘How did you come upon this, Vincent?’

‘I was trying to find a way to record glamour at a distance and worked this out as an extension of that theory. You know how it goes.’