‘I did something wrong,’ she said. ‘Something I shouldn’t have, but a victimless crime, you could say. Nobody would have needed to know, nobody would be any the wiser, eh?’

‘Except?’ Catherine prompted.

‘Except that it meant I found something out, and I now cannae say what without saying how.’

It was like talking to Duncan or Fraser. Promising them they wouldn’t get into trouble because you needed to know, but aware that a sanction might nonetheless be obligatory.

‘Come on, you can tell me. You’re halfway there.’

Laura made a nervous face, a change at least from the gloomy one that had permeated her day.

‘It was Thursday morning, at that café. After Cairns got his call. You remember you went outside to get a better signal, eh?’

‘Sure,’ Catherine encouraged. It was less about the signal and more about the background noise in the busy café. It had been her job to call Scotrail to order the closure of the station and demand that they stop the trains: not something you could afford any ambiguity over resulting from a clatter of crockery or a shriek of laughter in the background, nor something you wanted to sound like a half-arsed idea you’d just had over a bacon roll and a double espresso.

‘Well, while you were out there, Cairns nipped to the toilet before all the action kicked off. He left his phone on the table.’

Laura bit her lip.

They both knew the next part. She didn’t have to spell it out, though she did feel she had to excuse it.

‘You’d said to me a few minutes before, you know, what you wouldn’t give for that number.’

Catherine withheld a host of unhelpful responses, grateful again to her sons for training her to handle such situations.

‘I know it was wrong, I don’t need any lectures on the ethics of it. It’s just I feel like I’ve been treading water since I got here. Not living up to anybody’s expectations. I needed something in my locker. I wanted to be able to pull a rabbit from a hat, eh? Of course, soon after, I realised it was a bloody stupid thing to do, not least because this was a rabbit I couldn’t show to anybody. But the thing is, I need to show it to you. I saw the report on Tommy Miller yesterday, and the mobile number listed as being his wasn’t the one that called Cairns.’

‘Did you get a name?

‘No, I just looked up the last incoming call. The phone hadn’t identified it as an established contact: just a number.’

Catherine felt the familiar relief of recognising a squall unlikely to escape the bounds of its teacup. She wouldn’t be leaving her mobile lying about near Laura, right enough, but still, there was a simple enough explanation.