Knox frowned. This didn’t feel like the time for one of MI5’s most senior officers to be plane-spotting over cucumber sandwiches at the edge of the world. But, if Knox was entirely honest with himself, he didn’t mind as much as he should. He was tired. More tired than he should be. And it wasn’t the kind of tiredness that fourteen hours of sleep could fix. It was the kind that meant something fundamental in his life might have to change soon.

Knox had been sent all this way ‘for a chat’. Those had been the exact words James Holland, the director general of MI5 and Knox’s patron and friend of twenty years, had used during his brief London stopover.

‘A chat with whom?’ Knox had asked, sitting in Holland’s office, next to his own on the fifth floor of Leconfield House.

‘Sir Guy Northcott,’ Holland replied.

‘I recognise the name. The textile magnate.’

‘Whose advancements in industrial fabric design earned him a knighthood.’

‘Industrial fabric design?’

‘Uniforms,’ Holland said. ‘Fire-retardant, quick-drying, thermal. If you work for the armed forces, the police or the NHS you’ve worn something dreamed up by Northcott.’

‘Are we putting in an order for the Watchers?’ Knox asked.

The Watchers were MI5’s leg men, a combination of courier and street spy the Service used to monitor low-level targets. For years, Knox had been trying to stop them wearing their unofficial and highly recognisable livery of dark grey suits and beige mackintoshes, with little success.

Holland ignored his deputy’s joke and continued. ‘It’s a rather delicate matter, actually. Ever since Golitsyn defected and spilled the beans about the Cambridge traitors, the Americans have been getting increasingly paranoid about undocumented people sneaking around the place.’

Knox could sense the irritation starting to slip through Holland’s words. The DG had more than enough to deal with at home and, unusually for MI5, abroad, without jittery allies adding to it—he needed someone to take whatever this problem was off his plate, and that someone was Knox.

‘What’s that got to do with Northcott?’ Knox asked.

‘He officially retired five years ago. Fancied travelling the world on a quest for global peace and understanding, according to an article the Telegraph wrote about it. He settled on Vancouver Island, spending his days hiking in the woods or flying around in his seaplane. The problem is, he never files a flight plan and almost always has a young male passenger with him, a different one each trip who apparently is never seen again.’

‘So the Americans think he’s up to no good?’

‘The Americans don’t trust anyone interested in universal brotherhood. Concerns have been quietly raised. They’ve never been happy about the Soviet Union being so close to them over there, or about how open their border with Canada is.’