‘Bob,’ she said firmly. ‘You’re havering. What’s the script?’

‘He said there’s a package in the left luggage at Central station. Said it was likely to prove explosive.’

‘A bomb at Central?’ Catherine said. ‘Is he placed to know something like this?’

‘This bastard? You never know. But he didn’t say it was a bomb. “Likely to prove explosive”: those were his exact words. I told you, he never gives you anything straight. It’s always wrapped up in shite and barbed wire. Whatever it is, I’m not taking any chances. We need to evacuate.’

Evacuating Glasgow Central station on a weekday morning was no trivial matter; it wasn’t like you could just hit an alarm somewhere and get everybody to muster at an assembly point. Not only did they have to close the station, but they had to stop all the trains heading into it. This took the cooperation of the Transport Police, as well as authorisation from Scotrail, which Catherine, as detective superintendent, had to procure using her sternest yes-I’m-serious telephone manner.

Nobody who had regularly travelled into Central by train would be particularly surprised or alarmed at finding themselves sat there unmoving, parallel to Bridge Street, a frustratingly few hundred yards from the platform. However, what might tip them off that something extraordinary was afoot was the fact that they couldn’t pass the time as usual staring across towards the Citizens Theatre and reminiscing about childhood trips to the panto, because their view was blocked by half a dozen other stationary trains. And those were just the ones on final approach; further services were being halted at every major junction, with trains held at commuter stations all the way down each line.

Catherine didn’t have to worry about them, though: they were somebody else’s problem, safely contained by the simple expedient of switching a few signals to red. Clearing several hundred people out of the station itself was a bit more logistically complex.

With no time to waste, they had to pull in every officer who could get there inside five minutes, which meant there was no room for egos or quibbles over rank and demarcation. They were all bobbies now, Catherine and Laura stewarding passengers towards the exits and checking for strays alongside the uniformed PCs.