‘Hang on,’ he told them. ‘We’re really close, I just have to check something. Stay here. Oh, and remember what I told you if security shows up. Don’t tell them my name, and don’t tell them where you’re going.’

Viva held up her hand. ‘Um, Jack? I can’t find Baker House on my map …’

‘Just a second,’ he said, but his words were lost in a sudden chorus of phones buzzing, beeping and pinging. People around them fumbled for their devices, and Claire checked hers out of habit. Nothing.

But the people around them whooped, cheered, high-fived and … began to dance. All their phones were blaring out a song Claire recognised. Most of them had some kind of glow-in-the-dark things that they pulled from their pockets, and within seconds it was a full-on instant rave.

Their little group was an island of clueless in a sea of moving, jumping bodies … and suddenly, she didn’t see their tour guides anywhere. They’d just melted into the crowd. Gone.

Viva’s eyes were huge, and she was clutching all her official MIT loot to her chest as if someone might want to rip off her maps and binders. She crowded closer to Claire as a guy with huge holes in his ears and a shaved head began kangaroo-jumping around near them. The noise was deafening.

Claire spotted the campus security uniforms approaching, and pointed, and Viva gasped and looked as if she might faint. ‘Jack!’ she yelled, and turned in a circle, staring wildly. ‘Jack, they’re coming! Jack!’

But their tour guide was nowhere to be seen, and now, as more campus security descended, the flash-rave broke up and students began scrambling away in a hundred directions … leaving their little tour group frozen and stunned.

There was no sign of their guide anywhere.

Claire, whose survival instincts were a lot more finely honed, had been prepared to cut out, but Viva’s shaking hand on her arm prevented her from following the upperclass students, and before she could get Viva to flee with her, it was too late. There were three security guards flanking them, frowning and looking very serious.

‘Okay, you know this area’s off limits,’ one of them said. ‘Names!’

There was a confused babble of voices, and he cut them off with an impatient gesture and pointed to Claire.

‘Claire Danvers,’ she said. ‘But we were taking a tour. We didn’t know it was off limits.’

‘Likely story, Miss Danvers. If you were on a tour, where’s your guide?’

‘Um …’ Viva held up her hand. ‘He left? I’m Viva Adewah.’

He made notes. ‘Uh huh. Name of the guide, for the records?’

‘Um, I don’t know. He took off and left us here!’

The three security men exchanged a look, and the centre one made another official-looking note in his book. ‘And where were you headed?’