Four o’clock arrived, with still no sign of Ismail. Gessen’s dread rose as the minutes ticked away. They couldn’t wait any longer. It would soon be dark, and the absence of a signal from Ismail’s wrist monitor was a bad sign. Either he was too far away and out of range, or he’d fallen into one of the many crevasses that ringed the valley. That Ismail was lying bruised and bloodied at the bottom of a ravine didn’t bear thinking about.

When Gessen first acquired the property, it was apparent from the surveyor’s report that the grounds contained several potentially hazardous areas. But long before he enrolled his first patient, every precaution was taken to prevent a serious mishap. In his twelve years of running the clinic, not a single patient had been injured – with the exception of the odd bump or bruise. But an excellent safety record didn’t mean that Ismail wasn’t lying wounded – or dead – at the bottom of a drop-off.

From the privacy of his office, he telephoned the local police, who informed him they would coordinate the search with Mountain Rescue. As Gessen hung up the phone, a pain stabbed his gut. Time was of the essence. Darkness was moving in and the temperature falling. With the ever-deepening layers of snow in the mountains, if they didn’t find him soon, Ismail would die of exposure. Gessen sank into the chair. How did he slip away? It was nearly impossible for someone on the staff not to know where a patient was at any given moment of the day or night.

Nearly. That nebulous word held such immense room for error that his hands shook. To the casual observer, the pastoral setting and open spaces of the clinic grounds belied the fact that it was a virtual prison. A carefully designed set-up that monitored his patients’ every move, while giving the impression of boundless freedom.

He pulled on his coat and headed to the chalet that housed his security team. They’d already viewed the tapes from the cameras and found nothing of concern, but he wanted to see the footage himself. Icy pellets of snow fell from the sky, and a chilly mist shrouded the valley. It would be snowing hard in the mountains.

Walter Keller, his head of Security, greeted Gessen with a grim look. In the operations room, they scanned the sixteen screens with views of the property. There were no cameras in the patients’ rooms, but every other square millimetre of the grounds was covered.