He knew Rhona wasn’t keen on flying either, but she had somehow convinced herself of its viability via science.

Science didn’t work for McNab.

Skye dropped beneath him and, the day being clear, he had a full dose of what he was leaving behind. Having seen the Cuillin ridge outlined on an Ordnance Survey map, courtesy of Jamie McColl, McNab now saw it in all its stark reality.

Why the fuck would anyone want to climb that?

The peninsula where Rhona thought the girl, Seven, had headed, with its twin flat tables, looked to McNab like a lunar landscape, while round its edges the sea beat its power against huge cliffs and shattered coves.

As the co-pilot pointed out all the relevant locations, McNab said nothing, seeking only the bridge that led to the mainland, while reminding himself of the motorbike trip with Rhona he’d taken to get there.

Gradually all talk ceased and, ignoring the windows, McNab contemplated instead the body bag he was bringing home. Rhona had called him after her chat with the Norwegian and he had learned another piece of the mystery that seemed to surround Private Peter Galbraith, if it was indeed him zipped up inside the body bag.

The post-mortem had been arranged to swiftly follow their arrival. McNab preferred the idea of interviewing Harry first, but apparently that had been organized for the afternoon, Harry’s presence at 2 p.m. being guaranteed by Ellie.

So the PM it was.

Although McNab disliked the mortuary and all that happened therein, he was curious to find out whether the estimated time of death might fall into the timeline of Watson’s own demise. If the pathologist turned out to be Sissons, he wouldn’t make life easy for McNab, but the acerbic doctor’s caustic remarks could be dealt with if there was something interesting to learn from them.

As they approached the River Clyde and the signs of human habitation became more marked, McNab found himself relaxing. The cloud grew thicker as they neared Glasgow, and when the rain began to hit the windscreen, he decided that civilization, however damp, was very welcome.

At touchdown they were met by both an ambulance and a police car. McNab, thinking he’d spent enough travelling time with a corpse, opted for a trip to the morgue in the police vehicle instead.

‘DI Wilson wants you back at the station,’ he was informed as he climbed inside.

‘But I was told McArthur wasn’t coming in until this afternoon?’

‘Change of plan,’ his driver told him. ‘He’s at the station now.’

‘Any idea why?’

The driver shook his head. ‘Although I hear he’s pretty jittery.’

McNab wondered if that was caused by a lack of heroin or a fear of reprisal – or maybe both.