Finn was his closest ally growing up. His sister Georgia was two years older and had her own gaggle of giggling girls to hang out with. He and Finn played together every day. Elaborate games of make-believe. Of cops and robbers, of scientists and laboratories – their disparate interests clear from an early age, but each happy to play the part created by the other. Finn got Robin through school, helping him out with homework, science and maths a mystery to the practical Robin. And Robin was there for Finn. Bullies stayed well clear from the skinny glasses-wearing nerd, knowing that his mate Butler wasn’t afraid to throw around a fist or two.

They stayed close, even when they both went away to uni. Finn got a first in physics, then a doctorate. He landed plaudits and gained respect from his peers; Josie always spoke about him with pride. Robin scraped a lower second, then joined the force. But despite feeling in his shadow, he’s always been proud of his friend.

He finds it hard to reconcile his calm, nerdy, slightly naive mate with this bloody crime scene. He needs to get in there, talk to him, find out what’s going on. There is no way Finn killed someone. No way.

But as they drive into the car park, his feelings of dread intensify. The small crowd of press is bigger and clamours to see into the car as they pass; a large ambulance waits on the ground floor. And where before first responders were standing around waiting, almost bored, now there is activity. People are milling round computers, talking in frantic, hushed whispers. A DC runs up to the car, ushering him towards Craig.

‘Over the last half hour he’s got louder,’ she says. ‘I tried to talk to him but he started shouting.’

‘Saying what?’ Robin asks. They walk closer to the van.

‘I haven’t been able to make it out. But the nearer I got, the more pissed off he seemed.’

They stop about five metres from the van. It’s silent again now; the car park goes quiet as everyone waits. Then Finn appears at the window.

Robin involuntarily gasps. Finn’s face is gaunt, cheekbones protruding sharply. He isn’t wearing his glasses and he screws up his face, squinting out. His hair is in disarray, and Robin can see traces of something dark across his chin and face. Blood, he assumes.

He feels a nudge from Craig next to him.

‘Finn,’ Robin shouts. ‘Are you okay?’

‘Robin?’ Finn’s face rumples with confusion, as if he hadn’t realised that Robin was there. He glances back into the van.

‘I’m here, Finn. Your mum, too.’ Robin hears footsteps behind him, as Josie walks up to his side.