Dr Graham patted the clay-covered skull. ‘Our friend here was male, Caucasian, and about forty years old. The remains on your roof, on the other fingertip-less hand, are definitely female, mid sixties, five foot three, and her second and third lumbar vertebrae were surgically fused at some point: that might be worth chasing up? ’

Logan glanced back at the pale-grey bones. ‘How did she die? ’

‘My life coach says I should always turn a negative into a positive. So: there are excellent opportunities there for further discovery.’

‘You have no idea, do you? ’

She scrunched up one side of her face. ‘Well, there’s no knife marks on the bones, or signs of blunt-force trauma, or bullet holes. . . To be honest, it’s impossible to tell, especially without the rest of the remains. We’ve got nothing below the knees and we’re missing both arms too – he could have hacked them off and she bled to death. Maybe he drowned her? Suffocated her. There’s no hyoid, so she could’ve been strangled. Or he stabbed her in the stomach. Or made her drink bleach. Or—’

‘Enough, OK. I get the picture.’

Dr Graham shrugged. ‘If you want, I can send a sample off to that friend of mine in Dundee? ’

‘Do it.’

She picked the left femur from the plastic sheet and hefted it like a club, tapping the hip joint on the palm of her hand. ‘I’ll just need you to sign a couple of release forms. . .’

‘Yeah, sorry.’ Logan sat on the edge of Dr Forsyth’s old desk, mobile phone pinned between his shoulder and his ear, hunting through his jacket pockets for a pen. Bloody things must be hiding. He pulled out his notebook, his car keys, his warrant card, laying them on the desk beside him. Then a handful of business cards, two packs of individually sealed blue nitrile gloves. Then that white DL envelope Hissing Sid gave him, and then the brown one. . .

They sat on the Formica desktop like tombstones.

A female voice dribbled into his ear. ‘. . .there yet? ’

Blink. ‘Erm . . . I think so.’ The pen was lying sideways in the bottom of the pocket. He pulled it out and got her to repeat the authorization number and scrawled it down in his notebook, along with the Fiscal Depute’s name and the time and date. Covering his arse, just in case. ‘Thanks.’

‘And this isn’t going to take a chunk out of budget? ’

‘Pro bono, apparently.’ He stared down at the tombstones. Puffed out his cheeks. Then picked up the white envelope and tore it open.

‘Really? Is this a regular thing, or a special favour, because the PF would definitely use this stable isotope thingy a lot more often if it’s free.’