Peter Longhorn was talking about quantum entanglement but she couldn’t take it in. Her body vibrated with the buzz from the lights and it made her feel exposed, as if her hangover had worn away her skin, dissolved the border between her and the universe so that she might float apart any second and join the great mess of chemical existence.

Entanglement was the kind of mindfuck she usually loved in physics, that entangled pairs of subatomic particles were intrinsically linked by their quantum state even when separated. Measurement of one particle’s state collapsed the function and gave information on the other’s state instantaneously, breaking the rule that limited transfer of information to the speed of light. And that was just the start. Digging into the maths there were caveats and inconsistencies, violations and arguments about what rival theories meant, even the idea that time could be a side-effect of entanglement. It was all about perspective, where you viewed the universe from, how you observed it and interacted with it, how cause and effect played out on every level, from quarks to galaxies.

Right now, her perspective was that if she didn’t get some Irn Bru soon she might pass out.

She watched Longhorn with narrow eyes. He was tall with an air of authority, but without being a dick about it. He had a navy shirt tucked into dark jeans, pointy leather shoes, a cut above the sartorial elegance of other staff who wore mostly Star Trek T-shirts and trainers. He was mid-thirties, short blond hair and clean-shaven. And he was Mel’s Director of Studies, a token role in her case, since the DoS only got involved if a student was skipping classes or failing.

The class ended and everyone shuffled out, Xander nodding again at Hannah. He was about to come over and speak to her but seemed to have second thoughts, turning away through the doors.96

Dr Longhorn shuffled papers together and closed his laptop as she approached. Her head was thumping and her eyes were heavy.

‘Dr Longhorn,’ she said, swinging her rucksack onto her shoulder.

‘Peter, please.’

She nodded even though it made her cringe. ‘I was wondering if you’d seen Melanie Cheng recently?’

‘I could ask you the same question.’

‘Really?’

‘She had an appointment to see me the other day, never showed up.’

Hannah noticed his wedding ring, how long and thin his fingers were.

‘What was the appointment about, if you don’t mind me asking?’

‘I have no idea. She emailed to set it up but didn’t say why.’

‘She emailed you?’

‘Is something the matter?’

Hannah tried to quell her stomach, she felt hungry and sick at the same time. ‘She’s gone missing.’

Peter stopped tidying. ‘What do you mean?’

‘No one has seen her for three days.’

‘Did she go back home?’

‘When I say no one, I mean no one.’