Her first exam was in the dining hall, and everyone gathered at their lockers putting their bags away; the rules about what they could and couldn’t take in with them were displayed on pretty much every door and notice board in the building. There was a lot of murmured panic as friends compared nerves, competing – or so it seemed to Kym – to be the most unprepared for the ordeal ahead. She could see Evie Wilson shoving her bag up onto a shelf, picking up a pencil case, then slamming her locker door shut. As she did, something fine and vivid slithered to the floor, briefly catching the light as Evie turned and headed down the corridor. No one else seemed to notice.

Kym caught up with her just as the dining hall doors were opened.

‘Hey,’ she said, tapping Evie gently on the elbow, ‘you dropped this.’

‘Oh.’

It was a silver shoe, a ballet slipper, on a thin red ribbon. Kym held it up and it danced in the air.

Evie held out her hand. ‘Thanks,’ she said, and Kym released the makeshift bracelet, letting it pool into Evie’s palm.

They all had them, of course. Lucky charms, dangling from bags and pencil cases, or hanging from a necklace, hidden beneath a school shirt and tie.

‘Not that you need it,’ said Kym.

‘Well.’ Evie tucked the slipper into her pocket. ‘It can’t hurt, right?’

‘I suppose.’

‘You mean you’ve not brought anything with you?’

Kym lifted her pencil case – transparent as per the rules, as if they were all going through airport security or something – and shook it, rattling around in the bottom there was a piece of flint. It was flat and grey, shaped liked an arrowhead and worn smooth by the sea, with a natural hole running through it, about the size of the tip of her little finger. ‘My gran,’ she said, as if that explained everything. ‘I’ve had it for years.’

It had been that last summer between primary and big school. They’d been for a walk on the Long Sands and Gina had found the stone, wiping it clean and insisting Kym keep it with her for luck. She’d dropped it into her school bag when she’d got home, and every time since, when she’d transferred all her stuff to a new bag, she had picked it up and thought about chucking it away. She never had, though, always dropping it in at the last moment with all her usual bits and pieces. This morning she’d made a point of hiding it away inside the pencil case.

‘A rock,’ said Evie. ‘Nice.’

‘It’s a hagstone,’ said Kym. ‘If you look through them you can see into the other world.’

Evie looked sceptical. ‘And can you?’

Kym smiled. ‘If I can, it looks disturbingly like this one.’