There was surprisingly little to search through. The most interesting result was a list of coordinates – about fifty of them – in a program that clearly had something to do with the AME controls. Curiously enough, the GPS coordinates were all nearly identical, with just a few differing numbers at the end of each one. Whatever these things were, they were in almost exactly the same place.

‘Guys,’ she whispered into the radio. Mark saw her, and turned his own radio back on. ‘I think I know what those land-mine-shaped objects are for.’

‘Oh,’ added Mark, ‘and the guy we mentioned is now dead. Good job he fell asleep on duty – the shield was one button away from going up.’

The others expressed surprise, but Kate stopped listening. She scanned through the contents of the man’s laptop, and found nothing more of use. In the background, Raj said something about an interesting find in the library.

‘Can’t see anything useful here,’ she whispered.

‘Right then,’ said Mark, raising the butt of his assault rifle, ‘if you’ll allow me…’

‘No, don’t just smash it. They’ll be clever enough to put the pieces back together. This needs to be really destroyed… whisky’s flammable, right?’

‘What, so I should pour my precious single malt over a computer and set it alight? Besides, we’d have no way of putting out the fire once it starts. Let’s get some acid.’

He headed for the exit, not bothering to check the corridors as he walked into them.

‘Acid?’ asked Kate.

‘Yeah, from chemistry.’

‘They never had anything that could melt a computer…’

‘No, they didn’t. But if you do your research, you can combine the boring stuff to make a corrosive solution. And it’s corroding, not melting.’

Kate followed Mark around the next corner, wondering what kind of person Mark could have been in a different life. He was capable, intelligent, determined and had no diagnoses that she knew of. Oakenfold wasn’t designed for people like him, even though life had led him there.

‘The lab’s the other way,’ said Kate.

‘Staff room first,’ Mark replied, pointing at the next door down.

‘Looking for more drink?’

‘Looking for keys. They never kept chemistry stuff in unlocked cupboards.’

He opened the door to the staff room. It was windowless, and pitch black. Mark, without a moment’s thought, switched on the light.

The room lit up to reveal a dusty, lifeless room. Empty mugs of tea rested on tables full of teachers’ marking, the writing on the staff whiteboard had faded away, and a collection box for school pantomime tickets had collected a year’s worth of dust.

But Mark was worried.

‘Someone else is here,’ he whispered. ‘That other guy had a friend.’