Over the next few days, the police made several visits to Scotland Street, and the neighbourhood, now abuzz with speculation, became accustomed to the sight of white police cars parked in the street. Throughout the vicinity, posters appeared on the railings bearing the legend Have you seen this woman? Underneath was a photograph of Irene, followed by a brief invitation to any member of the public who had spotted her after her recent disappearance at the foot of Scotland Street to contact the Gayfield Square Police Station without delay.

Stuart, on compassionate leave from the Department of Statistics, underwent several searching interviews with police officers, while Bertie and Ulysses were looked after by a woman police constable in the room next door.

‘I’m sorry that we have to ask this question, sir,’ explained the senior police officer who had taken over the case, ‘but is it possible that your wife was perhaps seeing somebody?’

Stuart looked blank. ‘Seeing somebody?’

‘You know, sir, having an affair?’

Stuart opened his mouth to say something; but he could not speak.

The police officer was sympathetic. ‘As I said, we don’t like to pry into these private matters, sir, but it’s often the case that missing persons have been seeing somebody else and have simply gone off with that person. We had a case recently – and I won’t mention any names, of course – where this woman went missing and her husband had no idea that she was carrying on with a man in Dundee. She just went off with him, without a word of warning. It was a total surprise.’

‘My wife …’ Stuart began, but then stopped himself. He had been intending to say, ‘My wife is not that kind of person’ – but he suddenly asked himself whether he really could say this, and he felt that he could not. He had remembered Hugo Fairbairn and the remark that Bertie had made about the relationship between Irene and the psychotherapist. ‘She really likes him, you know, Daddy,’ Bertie had said. ‘I think he’s her best friend actually. When Dr Fairbairn is sent to Carstairs, I’m sure that Mummy will visit him there.’ Stuart had smiled, and dismissed it as one of Bertie’s amusing little remarks, but then there had been that rather disquieting comment that Bertie had made about the appearance of Ulysses. Again, he had not paid much attention, but now the issue was being raised and it all came back.

Noticing his hesitation, the police officer gave a gentle nudge. ‘You can talk to us in complete confidence, you know. Nothing you say will go beyond these walls.’

Stuart nodded. He felt miserable; it was disloyal, surely, even to make the suggestion. ‘It’s possible she may have,’ he said at last.

The police officer looked away tactfully. ‘I see. And do you think that this affair is still going on?’