‘Why would Jacinda – Jane – be in Podgorica?’ He says this like a teacher who already knows the answer, and is trying to find out if I do too.

To help Zac steal my baby, I think, though I don’t quite understand how, or why they needed to be in Montenegro. ‘It’s just an instinct,’ I say.

‘It’s as if I’ve been hit on the head since I met you.’

‘If GCHQ ever fires you, you can write comedy.’

‘Go get something to eat, Holly. I’ll see what I can find.’

When Maxine and I come out of the kitchen half an hour later, George is sitting on one side of the sofa. I take the place on the other end, and Maxine wheels his desk chair across.

‘Okay,’ he says. ‘I found three more things. First, Holly, your instinct about Jacinda Molinero was right. Somebody checked into a five-star hotel in Podgorica under that name. It was a two-room, two-bath suite, and they stayed for ten weeks. Checked in on the eleventh of March, checked out on the twenty-sixth of May.’

‘Again, all inside the March-through-June dates when the CCTV was blocked,’ I say.

‘Yep. And the second thing is that there’s no CCTV for the hotel for those four months – same as the hospital. And here’s the third thing.’ He takes a piece of paper from the sofa arm beside him, then hands it to me. ‘I printed this for you.’

I turn it over. ‘Oh.’ It is a photograph. ‘Oh my God.’

The three of them are so young, so happy looking and beautiful and uncomplicated.

Zac, before Jane ran away from him.

Jane, before she ever knew she had a brother.

Eliza, before Zac broke her heart, then changed his mind and married her.

‘It was 1999, the UCL Summer Ball,’ George says. ‘From the university archives.’

Zac, twenty-four years old, is standing in the middle. One of his arms is around Jane, the other around Eliza. The two women look like Hollywood film stars, in their shimmering gowns, with their upswept hair.

‘We knew all three of them were at UCL at the same time,’ he says. ‘But I thought if I showed you the connection, it might help you to understand why Jane was with Eliza in Podgorica. They were old friends. They met in halls in their first year. Jane must have been supporting Eliza for the birth.’

‘That partly makes sense,’ I say, ‘but it’s also weird. Don’t you think? I mean, Jane supporting a woman who’s having her ex-husband’s baby? It’s not exactly the basis for a thriving friendship.’

‘Perhaps Eliza didn’t tell her who the father was,’ Maxine says.

My cheeks lift and my eyes squeeze in doubt. ‘That doesn’t sound right.’

Maxine stands. ‘Holly, it’s been a difficult day for you.’

‘Yes.’ George reaches across and squeezes my hand. ‘I’m so sorry about your grandmother.’