The team at the Visual Images, Identifications and Detections Office were as good as their word. Soon after Geraldine arrived back at her desk, they sent her an image of Jessica and another woman seated beside her. Neither of the two women in the picture appeared to be talking, they both looked fairly glum and they were holding babies who looked around the same age. Geraldine studied the image of Jessica’s companion, an emaciated girl with lank blonde hair which she had probably dyed herself, because the dark roots were uneven. She looked fragile, and could have been anorexic, with her stick-like limbs and painfully thin body. Her face was covered in pimples and she had an unhealthy appearance. Geraldine wondered whether she might be a drug addict. Her large pale eyes were her only attractive feature. At a first glance it was difficult to see what smartly-dressed Jessica might have in common with the thin girl, other than their babies possibly being the same age, and the fact that they were both somehow isolated from the group of women who were chatting a few seats away.

Geraldine wasted no time in organising a team to question every midwife, hospital and local doctor’s surgery in the vicinity, hoping to discover details of Jessica’s companion. Armed with the photograph, Geraldine set off to speak to some local gynaecologists herself. She showed the photograph to every member of the team attached to the maternity unit at the hospital in York, explaining that she was looking for a young woman who had given birth around six or seven months earlier.

Whoever she asked returned the same answer. ‘I’m sorry, I don’t recognise her.’

‘Mothers do sometimes look a bit different when we see them in here,’ one of the gynaecologists added, with an apologetic smile. ‘They’re not always at their best, in terms of grooming.’

The other members of Geraldine’s team had similar responses to their enquiries. It seemed that Jessica’s friend had not given birth in York. They would have to widen the net if they were going to find the unknown woman who had befriended Jessica. But when Geraldine showed the photograph to Jessica’s health visitor, she finally received a positive response.

‘Oh yes, I know who that is,’ Mary said at once. ‘It’s –’ she broke off and paused, frowning.

Geraldine waited, hiding her impatience.

‘Yes, it’s coming back to me. Her name’s Ella,’ the health visitor said at last.

‘Ella?’

‘Yes.’

‘What’s her other name?’

‘Just a minute.’

Mary went and fetched her laptop.

‘Ella Wilson.’ She read out an address. ‘I never forget a face, but names do sometimes escape me. I see so many of these young mothers,’ she explained apologetically. ‘And when I haven’t seen them for a while, it’s easy to forget their names.’

‘When did you last see Ella?’

‘I haven’t seen her for at least three months.’