Driving back to her Barbican flat, Carol was barely conscious of the traffic that flowed around her. Although she liked to think that, professionally, she always expected the unexpected, the course of the afternoon’s proceedings had caught her completely unawares. First, the appearance out of the blue of Paul Bishop. Then the bizarre turn the interview had taken.

Somewhere around the elevated section of the Westway, Carol’s bewilderment started to develop an edge of irritation. Something stank. An ELO’s job wasn’t operational. It was analytical. It wasn’t a field job; she’d be flying a desk, sifting and sorting intelligence from a wide variety of sources across the European Union. Organized crime, drugs, the smuggling of illegal immigrants, that’s what she’d be focusing on. An ELO was the person with the computer skills and the investigative nous to make connections, to filter out the background noise and come up with the clearest possible map of criminal activity that could have an impact on the UK. The nearest an ELO should ever come to primary sources was to cultivate officers from other countries, to build the kind of contacts that ensured the information that made it through to her was both accurate and comprehensive.

So why did they want her to do something she’d never done before? They must have known from her file that she’d never worked undercover, not even when she was a junior detective. There was nothing in her background to indicate she’d have any aptitude for taking on someone else’s life.

In the stop-start traffic of the Marylebone Road, it dawned on her that this was what troubled her most. She didn’t know whether she could do this. And if there was one thing Carol hated even more than being blindsided, it was the thought of failure.

If she was going to beat this challenge, she was going to have to do some serious research. And she was going to have to do it fast.

Frances was chopping vegetables when Tony walked in, Radio 4 voices laying down their authoritative counterpoint to the sound of the knife on the wooden board. He paused on the threshold to appreciate something so ordinary, so comfortable, so relatively unfamiliar in his life as a woman preparing dinner in his kitchen. Frances Mackay, thirty-seven, a teacher of French and Spanish at the high school in St Andrews. The blue-black hair, sapphire blue eyes and pale skin of a particular Hebridean genetic strain, the trim figure of a golfer, the sharp, sly humour of a cynic. They’d met when he’d joined the local bridge club. Tony hadn’t played since he’d been an undergraduate, but it was something he knew he could pick up again, an accessible part of his past that would allow him to build another course of brickwork in his perpetual facade; what, in his own mind, he called passing for human.