Vidor considered this. Should he tell them that Ismail had made a point of rubbing him the wrong way and that he took special pains to avoid him? Better not. The sensation that prickled his skin whenever that annoying lad entered his orbit was too subtle to put into words. So was the vague sense of threat he felt at the idea of Ismail sleeping on the other side of his bedroom wall. The police might count it as a mark against him. Perhaps even wonder whether he’d had something to do with Ismail’s disappearance. Preposterous, of course, but you never knew with the police, always so eager to point fingers at the innocent.

‘Two days ago, I believe, was the last time I saw him. It might have been a Tuesday, or perhaps a Wednesday? Late afternoon. Around four, it could have been. Or five, though it’s hard to say exactly.’ He looked at his interlocutor. ‘You may have noticed the absence of clocks.’

The two officers exchanged a glance. ‘So, you and Mr Mahmoud were not on friendly terms?’

‘I didn’t say that.’ He bristled. What were they implying? ‘But I’m not here to socialise, and I don’t make a habit of chatting with the other patients.’ He examined a patch of abraded skin on his wrist. He must have scraped it yesterday when he slipped on the icy path. ‘I’m supposed to be resting.’

Officer Müller checked her notes. ‘One of the other patients said she saw you talking to Mr Mahmoud on the afternoon he disappeared.’

Vidor’s head snapped up. Who would have told them that? ‘Not that woman Hélène, I hope.’ He tapped his temple. ‘Mad as a hatter, that one.’

Officer Müller fixed him with a clear-eyed gaze, waiting for him to say more, perhaps even hoping to entrap him in a falsehood. Little got past this woman, that much was clear.

When nothing more was forthcoming, she closed her notebook. ‘Thank you, Mr Kiraly. You’ve been very helpful.’

‘Actually, it’s Professor Kiraly,’ he said. ‘I’m a Cambridge don, and was recently awarded an OBE from Her Majesty the Queen.’ He didn’t want her thinking he was a drooling idiot with scrambled eggs for brains. ‘Very sad, of course, what happened to that boy, but what could you expect?’ He’d heard the rumours. ‘Deeply depressed, apparently, and pining for some girl back in England. The young can be so impulsive, can’t they? At that age, everything is so dramatic.’ He briefly locked eyes with the younger officer. ‘Are you familiar with the concept of l’appel du vide?’

The officer pursed his mouth.

‘The call of… emptiness?’ This from Officer Müller.