He considered this, then put his helmet on the table and joined the queue. At the party, he’d struck me as hyper-intelligent, if a little sheltered. He was working on the technology for mass holographic deception. Talent leads you on strange journeys. At the party he had shown us a photo on his phone: it was Tehran’s skyline at dusk, only with a face denoting the Prophet Muhammad rising a mile high over the downtown office blocks. Joanna seemed impressed. I had bridled, ignoring the jawdropping aspects of this and arguing that most Iranians were too secular and astute to care. ‘Well, this was what we were tasked with,’ he said.

By the time he returned, splashing down a mug of Nescafe, his memory had done some work.

‘You’re Elliot.’

‘That’s right. We met at Hugh Stevenson’s fortieth.’

‘Do you know where Joanna is?’

‘No. I’d like to find out. Why did you contact her parents?’

Marsh breathed deeply. I smelled fresh aftershave.

‘I was questioned about her, at work. On Monday afternoon. I was taken for what they said was a routine security check. They were very interested in Joanna, whether I’d had contact with her since she left, the nature of our relationship.’

There it was, I thought: the creep of an intelligence agency turning against you. My suspicion was that they knew the answers to those questions. They were shaking him up to see what came out. I had no idea why.

‘And have you had contact?’

‘No.’

‘What’s the nature of your relationship?’

‘We’re friends,’ he said, cautiously.

‘When did she leave?’

‘April.’

‘Know why?’

‘No.’

‘Escorted out? Leaving party?’

‘Definitely no party. I don’t know if she was escorted. Next week her unit was shut down.’

‘What unit?’

‘I really don’t know much, and I can’t say much. I didn’t work with her. And … You know what it’s like.’

‘Shut down suddenly?’

‘Overnight.’

‘Do you think it had been compromised?’

‘I don’t know.’

‘Where did Joanna go after leaving?’

‘I’ve no idea. That’s what got me worried. That and the interrogation.’

‘You’d tried to contact her.’

‘Of course,’ he said. ‘What’s your involvement? Why did they think you were connected?’

‘What do you mean?’

‘The security officer asked about you.’

That gave me a lurch. Something ominous was coming into focus, but it was focus I wanted.

‘What did he say?’

‘He asked whether Joanna had mentioned you, if I thought the two of you were in contact. I said I had no idea. What’s going on?’

I thought of the tension around my recent debrief, the security interview, the confiscated phone.

‘Was the man who questioned you someone you’d seen before?’ I asked.

‘Never.’

‘What did he look like?’

‘Quite old; maybe sixty or so. No name.’

‘Did it seem like in-house security?’