The lights were on a thirty-second timer. As he waited for them to turn off, he considered what might have interrupted the infrared beams that criss-crossed the garden to trigger them. It would be a cat, he thought, or a fox, or a piece of overgrown foliage waving in the wind. And after a few seconds the lights were indeed doused and the room returned to darkness.

But now Hoffmann was wide awake. He reached for his mobile. It was one of a batch specially produced for the hedge fund that could encrypt certain sensitive phone calls and emails. To avoid disturbing Gabrielle – she detested this habit of his even more than she hated him smoking – he switched it on under the duvet and briefly checked the Profit amp; Loss screen for Far Eastern trading. In Tokyo, Singapore and Sydney the markets were, as predicted, falling but VIXAL-4 was already up 0.3 per cent, which meant by his calculations that he had made almost $3 million since going to bed. Satisfied, he turned off the device and replaced it on the nightstand, and that was when he heard a noise: soft, unidentifiable, and yet oddly disturbing, as if someone was moving around downstairs.

Staring at the tiny red dot of light of the smoke detector fixed to the ceiling, he extended his hand cautiously beneath the duvet towards Gabrielle. Lately, after they had made love, if she couldn’t sleep, she had got into the habit of going down to her studio to work. His palm traversed the warm undulations of the mattress until his fingertips brushed the skin of her hip. Immediately she muttered something unintelligible and rolled her back to him, pulling the duvet tighter around her shoulders.

The noise came again. He raised himself on his elbows and strained his ears. It was nothing specific – an occasional faint thump.