But his attention was fixed on something outside. Gessen turned to see what he was looking at, but there was nothing there. Just the usual jagged peaks, softened by a blanket of snow.

‘I feel no differently than the day I arrived,’ Vidor said. A muscle twitched in his jaw. ‘Perhaps a trifle more rested and well fed, but as for my mood, or my personality, I feel the same as I always have.’

Gessen tried to catch his eye. ‘Do you know why you attacked that man in Copenhagen, or the man in the village?’

‘I haven’t the slightest idea.’ Vidor had yet to look directly at Gessen. ‘Though in both cases, I’m convinced it was simply a matter of exhaustion and low blood sugar. Or perhaps a momentary disturbance in my frontal lobes.’ He examined his fingernails. ‘In all this time, we’ve never talked about the possibility of epileptic seizures as a mitigating factor.’

‘Your EEG and brain scan in Copenhagen were normal.’

‘A normal EEG in and of itself is not sufficient to rule out epilepsy,’ Vidor countered.

‘Have you ever wondered,’ Gessen said, rising to close the curtains and shut out the mountains, ‘why those two men? Or those particular occasions? I believe you have no record of previous incidents.’

‘Of course I don’t.’ His face darkened. ‘I’m not a ruffian.’

‘What about the lapses in memory and the sleepwalking we talked about earlier? Or the feeling you once described of someone standing next to you, just behind your left shoulder. What do you make of that?’

Vidor shrugged. ‘The brain shrinks as we grow older, and occasional memory lapses or quirks of proprioception are quite normal for someone my age.’

Gessen made a show of mulling over these assertions, before launching into it. ‘I have another explanation,’ he said, keeping his eyes on Vidor’s face. ‘I only suspected it at first, because it’s quite rare. But all the evidence points to the same conclusion. And during our last session, the final clue fell into place.’

Vidor crossed his arms over his chest. He looked placid, even bored.

‘While in a state of deep relaxation, you talked about your childhood. How you were born as a twin, and almost died, and were sent away to be raised by a woman in a nearby village. You mentioned what it felt like to watch your twin brother thrive under the care of your mother and sisters while you were cast aside. That your father was a monster who abandoned you to your fate as an outcast and a bastard, having accused your mother of having relations with another man, and insisting that you were not his son.’

Vidor removed a piece of lint from his trousers. ‘Have you gone mad?’ His thin smile looked pasted on.