‘Don’t be silly,’ said Phoebe. ‘It’s a Sofia by Vix – Ollie bought it for me in Nice – I wouldn’t leave it downstairs where she could get her hands on it.’

‘She’ being Victoria Jones – Phoebe’s stepmother.

‘So you must have gone upstairs to your room before you went down to the pool,’ I said.

Phoebe shrugged.

‘Yeah,’ she said. ‘Must have.’

Memory is unreliable, and it isn’t unusual for a witness to forget big chunks of the events that led to them answering your questions – even when things were fresh. Still, the obvious hole in Phoebe’s timeline was beginning to worry me.

‘Before the Americans turned up,’ I said, ‘was anyone in the basement with you?’

‘Like who?’

‘Like anybody.’

Phoebe frowned. ‘I was talking to someone,’ she said.

‘Do you remember who?’ asked Guleed.

‘Someone from school, I think,’ she said.

‘A school friend?’ asked Guleed.

‘No,’ said Phoebe and bit her lip. ‘An old person.’

‘Man or a woman?’

‘Man.’

‘A teacher?’ I asked.

‘No,’ said Phoebe firmly. ‘Not a teacher. You know, it’s funny, but I think he was a parent . . .’ she said.

‘What makes you think that?’ asked Guleed.

‘He was familiar – like I totally knew him from somewhere – but definitely not a teacher.’

‘And yet you didn’t recognise him?’ I said.

‘I did, but not so I could tell you who he was.’ She made a waving motion with both hands. ‘It’s like when you’re half-way to school and you can’t remember what you had for breakfast. You know you had breakfast, you know what you usually have for breakfast, but you cannot for the life of you remember what you actually had today.’

Doing a two-hander during an interview is all about rhythm; you and your partner shift backwards and forwards to keep the interviewee ever so slightly off balance. If they don’t have time to think about their answers, then they are more likely to blurt out the truth. Or at least contradict themselves enough for you to figure out what they’re lying about. Good cop/bad cop is the Hollywood version, simplified and sexed up for maximum drama in minimum screen time. Me and Guleed had spent a year, off and on, interviewing everyone from mad mechanics to surly bouncers – not to mention the thing with the police horse which I’ve promised never to bring up on pain of ninjutsu – so she knew that the next line was mine, which would have probably been me asking what his voice sounded like.

But my mind, ironically, went blank. Because all at once I knew who had been in the basement swimming pool with us that evening.

‘What did his voice sound like?’ asked Guleed.