'So they might be the killer'sl Or the killer's wife's, or his mother's, or their neighbour's, or granny's…' She wound down the window and flicked the dying remains of her cigarette out into the rainy sunshine. 'Damn things could be Gulf War surplus for all we know. Hell, they might not even have been prescribed locally!' said Steel, swinging around the roundabout onto Queen Mother Bridge. 'What we going to do? Phone up every doctor's office and pharmacy in the country and ask for a list of patients' names and addresses?'

'We could get them to narrow it down a bit; just ask for details of anyone with mental problems who's been prescribed the drug.'

'"Mental problems?"' She laughed. 'If they didn't have mental problems they wouldn't be on anti-bloody depressants, would they?' She looked across the car at him.

'Jesus, Lazarus, how'd you get to be a DS? They giving out sergeant's stripes free with boxes of Frosties?' Logan just scowled at the dashboard. 'Aye, well,' she smiled at him.

'When we get back to the ranch you can go find one of them tree-hugging wildlife crime officers to chase it up. Dead dog'll be right up their street. We'll start paying attention again if it comes to anything.'

HM Prison Craiginches was segregated from the outside world by twenty-four-foot-high walls, and a small black metal plaque saying, 'Private Property Keep Out', as if the razor wire wasn't enough of a hint. It was surrounded on three sides by residential streets – the houses festooned with burglar alarms – but on the fourth side there was nothing between the prison's north wall and the River Dee but the dual carriageway to Altens and a very steep bank. DI Steel parked in a bay marked 'Staff Only' and sauntered round to the front door, with Logan slouching along at her heels. Twelve minutes later they were sitting in a shabby little room with a chipped Formica table and creaky plastic seats complete with brown, slug-shaped cigarette burns. There was a tape recorder bolted to the wall, but no video, just the bracket and a couple of loose wires. They sat there for another five minutes, counting the ceiling tiles – twenty-two and a half – before Jamie McKinnon was finally shepherded round the door by a bored-looking guard. Logan popped a couple of fresh tapes into the machine and launched into the standard names, dates and location speech. 'So then, Jamie,' said DI Steel when he'd finished. 'How's the food? Good? Or is Dirty Duncan Dundas still wanking into the porridge?' Jamie just shuddered and started picking at the skin around his fingernails, hacking away at it until the quick showed deep pink underneath. It didn't look as if prison agreed with McKinnon; a thin sheen of sweat covered his face and there were dark bags under his eyes. He had a split lip and a bruised cheek.

Steel settled back in her seat and grinned at him. 'The reason we're here, my little porridge-muncher, is that there's a tiny problem with your alibi: someone saw you and Rosie Williams going at it like knives the night she got herself battered to death! How's about that for wacky coincidence?'

Jamie slowly slumped forward until his face was flat on the tabletop, his arms wrapped over his head.

'You want we should give you a couple of minutes to think up some new lies, Jamie?' asked the inspector.

'I didn't mean to hurt her 'Aye, we know that,' Steel pulled out her cigarettes and popped one in her mouth without offering them around. 'So why'd you do it then?'

'Been drinking… Down the Regents Arms… This bloke kept going on how she was nothing but a posh wank. No' even that…' He shivered. 'Followed him into the toilets and beat the shite out of him. Talking 'bout Rosie like that.

Like she was just a whore…'

Steel's reply came out in a cloud of cigarette smoke: 'She was a whore, Jamie, sold her arse on the streets for-'

'SHUT UP! SHE WAS NOT A WHORE!' He jerked up and slammed his fists on the table, making it jump. His face was flushed, eyes sparkling and damp.

Logan sighed and stepped in, playing the good cop. 'So you taught him a lesson for insulting your woman. I can understand that. What happened next? Did you go looking for her?'

Jamie nodded, eyes fastening on Logan, ignoring the inspector. 'Yes… I wanted to tell her: it has to stop! She has to stay home, look after the kids. No more going out on the streets…' He sniffed and wiped his nose on the back of his sleeve.

'What happened when you found her, Jamie?'

He looked down at his picked-at fingers. 'I'd been drinking.'

'We know that, Jamie: what happened?'

'We had this argument… She… She said she needed the money. Said she couldn't stop.' Jamie laid down another trail of silver on his sleeve. 'I told her I'd support her. I was getting something together, she wouldn't have to worry…

But she wasn't having any of it: kept going on and on about how I couldn't support her and the kids…' He bit his bottom lip. 'So I hit her. Just like that. And she started screaming at me. So I hit her again. Just to make her stop…'

Logan let the silence hang for a bit, while DI Steel dribbled smoke down her nose. 'Then what did you do?'

'Threw up in the toilet. Washed the blood off my hands … She was lying on the floor, all bruised… So I picked her up and put her to bed.'

Steel snarled. 'Put her to bed? That what they're calling it these days? "Putting. someone to bed"? What a lovely euphemism for strangling someone in an alleyway! Like fucking poetry that is.'

Jamie ignored her. 'Next day she was covered in bruises.

Threw me out. Said she never wanted to see me again. But I never meant to hurt her!'

Logan sat back in his seat and tried not to groan. 'It's Monday night we want to know about, Jamie. What happened on Monday night?'

'Went to see her, on the street.' He shrugged. 'Wanted to say I was sorry… show her I was making good money…

You know, from the fast-food jobs? I could take care of her and the kids. I loved her… But she wouldn't talk to me: said she had to earn a living… didn't want anything to do with me… had clients to see. I'd have to pay 'And did you?'

Jamie hung his head. 'I… Yes.'

DI Steel spluttered, sending ash sparking from the end of her fag. 'So you forked out to screw your ex? Jesus, how fucking twisted is that?'

Logan scowled at her. Then what happened, Jamie?'

'We did it in a doorway and… and I cried and told her I loved her and I was so sorry for what I'd done, but I loved her so much I couldn't stand to see her out there with other men…' His red eyes filled with tears. 'I was making good money now, I could do it, we could be together…' He wiped his eyes with the same silvered sleeve.

Steel inched forward in her seat, bathing Jamie in a cloud of cigarette smoke. 'She said no though, didn't she? She said no and you hit her. You hit her and you kept hitting her 'cos she wouldn't take a slimy wee shite like you back. You killed her, 'cos it was that or pay for it your whole life. Pay to screw her in alleyways, just like hundreds of other desperate wee fucks.'

'NO! She said she'd think about it! She was going to come back to me! We were going to be a family!' The tears were falling freely now, running down his chubby cheeks, his scarlet nose streaming as sobs shook his body. 'God, she's dead! She's dead!' He crumpled to the tabletop, shoulders heaving.

Logan's voice was soft. 'Did you hit her again, Jamie? Did you kill her?'

He could barely make out the reply. 'I loved her