Gessen leaned close to the console and studied the footage. Left to right, up and down, starting from the moment he’d left for Paris. There was Ismail leaving the main building after breakfast and heading towards his chalet, dressed in a dark jacket but minus the red knitted cap that all patients were obliged to wear outdoors. A minor rebellion that may have proved fatal. Fifty minutes later, he showed up in the northeast corner of the Zen garden, where he sat on a bench and stared into the distance.

‘Wait, what was that?’ Gessen pointed to camera number nine, and the entrance to the path into a copse of pines on the northern boundary. The recording appeared to judder for a moment and then reset.

‘Oh, that.’ Keller consulted the logbook on his desk. ‘There was a brief malfunction in that camera for about forty seconds. But it came right back online.’

Forty seconds? Plenty of time for a man to disappear. ‘How did that happen?’

‘No idea. None of the other cameras were affected. It could have been a power surge, or moisture in the casing. Marco went out there to have a look, but didn’t find any evidence of tampering.’

Gessen sank into a chair. How convenient that one of the cameras malfunctioned on the very day a patient slipped his tether. Coincidence? Or had someone interfered with the system? He closed his eyes as another pain cramped his gut. The day before Ismail was admitted, the entire staff had received a special briefing. Everyone knew that, security-wise, he was a sensitive case, and they’d been advised to take every precaution.

How was he going to tell Mr Mahmoud, a powerful and imperious man, accustomed to top-notch, impeccable service, that he’d lost his son? After the many assurances he’d given him that the clinic – even in the absence of razor wire – was as secure as any high-risk facility. Mr Mahmoud had specifically chosen Les Hirondelles. Not just for Gessen’s excellent psychiatric pedigree, but due to his absolute faith in Swiss ingenuity and technology. The man had entrusted him with his son’s life, and Gessen had let him down in the worst possible way.

As he turned away from the bank of screens, a familiar childhood terror flooded his limbs. The frantic drive through the night, as he lay hidden under a blanket in the back seat. Boarding a ship with his mother under the cover of darkness, where she held tight to his wrist as the harbour receded on the horizon. No explanation given for why they were leaving his father and older sisters behind.