Above the inky expanse of lawn, the moon was a silvery-blue discus that seemed to have been thrown at great speed through scudding masses of black cloud. The shadows of the big fir trees that screened the house from the road swayed and rustled in the wind.

Hoffmann took a few more paces out into the gravel drive – just far enough to interrupt the beam of the infrared sensors and set off the floodlights at the front of the house. The brightness made him jump, pinning him to the spot like an escaping prisoner. He put up his arm to shield his eyes and turned to face the yellow-lit interior of the hall, noticing as he did so that a large pair of black boots had been placed neatly to one side of the front door, as if their owner had not wanted to trail in mud or disturb the occupants. The boots were not Hoffmann’s and they were certainly not Gabrielle’s. He was also sure they had not been there when he arrived home almost six hours earlier.

His gaze transfixed by the boots, he fumbled for his mobile, almost dropped it, started dialling 911, remembered he was in Switzerland and tried again: 117.

The number rang just once – at 3.59 a.m., according to the Geneva Police Department, which records all emergency calls, and which subsequently issued a transcript. A woman answered sharply: ‘ Oui, police? ’

Her voice seemed to Hoffmann very loud in the stillness. It made him realise how visible he must be, standing exposed under the floodlights. He stepped quickly to his left, out of the line of sight of anyone watching from the hallway, and at the same time forward, into the lee of the house. He had the phone pressed very close to his mouth. He whispered: ‘ J’ai un intrus sur ma propriete.’ On the tape his voice sounds calm, thin, almost robotic. It is the voice of a man whose cerebral cortex – without his even being aware of it – is concentrating all its power entirely on survival. It is the voice of pure fear.