He’d only crossed the Atlantic twice after the war. Both trips had been to make nice with counterparts in American intelligence, and neither had gone particularly well.

The most recent trip had been for a joint conference with MI6 and the CIA and FBI eighteen months ago. Washington was in the grip of a long, hard winter, and after almost ten hours in the air Knox’s BOAC Comet was forced to spend another one circling Washington airport in a blizzard before air traffic control let the plane land. Knox had spent ten hours flying backwards in one of the rear-facing seats in the plane’s first-class compartment and avoiding making polite conversation with his fellow passengers, and the whole time circling Washington staring unblinkingly at the bright silver engine tucked under the wing that was barely five feet from him.

The conference was equally unpleasant. In fact, Knox was convinced the two American agencies were running a double act designed to discourage further visits from their British cousins. His meetings with the CIA were short and curt, and his round-tables and seminars with the FBI were interminably long and dull. His evenings were swallowed up with dinners and receptions full of people telling him how great a town Washington was.

Two days later, he was back at the airport for his overnight flight to London. The blizzard had lasted the whole time he’d been in Washington. He’d been on the last flight in, and he was getting the first flight out. As he sat in the departure lounge, watching the crew board the plane that would take him back to London—another Comet, painted white and silver, with a black slash reaching back from the cockpit along its sides, as if pointing the way home—his only hope was that the in-flight meal would be served early so he could get some sleep and start to forget the whole trip as quickly as possible.

The second thing that kept running through his head was where Bennett’s fear of discoveries like Bianchi and Moretti’s—and inventions like Pipistrelle—could lead.

The world of science fiction was full of societies where malignant forces watched over downtrodden populations, eternally hunting for traitors and the not quite loyal enough. But not the real world.

Spying, like war, had strict rules of engagement, and they were followed by most sides, most of the time. People were regularly trailed or tapped by intelligence agents, but only when necessary, not simply out of interest. Neither America, who probably had the money to attempt some kind of mass surveillance programme, nor Russia, who probably had the manpower, had ever tried something so ambitious. Even the deep, penetrating reach of the Stasi, Europe’s most invasive intelligence operation, was achieved more through myth and rumour than actual, active surveillance.

Would real science change those rules?