I’d nodded along with him, in utter ignorance, trying to keep my ad hoc researcher from going down an information technology rabbit hole. The only sums I was any good at were those that helped me acquire and kill targets. I used mathematics to judge range and angle; but the wisdom of the shot? There was no algorithm that could work that out for you. Autonomous weapons systems could tell you when to open fire, but not how to live with yourself once you had. For now, at least, someone always had to pull the trigger or press the button – and computers don’t have nightmares about playing God.

Despite international plaudits it looked like Rachel had published nothing in the four years she’d been at the university; she was camera-shy to the point of scopophobia and was, apparently, unmarried – a fact that did not pass unnoticed by Baaz. It took an effort of will to look at her faculty photograph – a low-resolution three-quarters-profile headshot – which was the only close-up image of her face we’d turned up. I’d last seen her a few days after her eighteenth birthday. She was in hospital, brought back from the brink first by me and then by Doc. The Rachel of my failing memory bore little resemblance to the confident professional staring out from that computer screen in Paris. But it was her for sure: olive skin, green eyes and a shock of black hair, shot through now with streaks of silver. I’d swallowed hard and realized my throat was dry.

‘You,’ Baaz had asked me in disbelief at the end of our joint investigations, ‘know her?’ I shrugged, feigning disinterest. ‘But … she’s brilliant. And she’s hot.’

I opened my eyes again to find the faculty secretary standing over me. She was more smoking angry than smoking hot.

‘Koma revi’it, delet shlishit miyamin,’ she said. I frowned and she repeated tersely in English the directions to Rachel’s office as she sat down again. I stood and thanked her, wincing as the wound in my shoulder flared up. I found the stairs she’d told me to take and climbed them slowly to the fourth floor, where the last flight emerged midway along a window-lined corridor. The sunset had faded but it wasn’t dark yet. The sky was sapphire blue, punctured by white pinpricks of the brightest stars.