‘Yes, I think I am.’ Carla sat down next to her and Nell shifted slightly away, aware she must smell of alcohol, fags and sleep.

‘Thanks for last night.’

‘You’re welcome. Thanks for coming up.’

Nell took another sip, this time braced for the heat.

‘I’ve been thinking,’ Carla said, her expression suddenly thoughtful. ‘If Mary has been targeting Eve, and was involved in Connor’s murder, I bet there’s something in the phone bills I got from the Telephone Unit that will identify her. I mean, stalkers – which is what she basically is – evolve. The contact they have with their victims has to be sufficient to sate their desire, so although originally happy with letters – maybe the odd glance through a front-room window – gradually that will cease to be enough. They’ll need more contact – braver contact, more direct – to get that same feeling of satisfaction. Eve started to get the letters months ago, right?’

Nell’s hangover was struggling to keep up so she just nodded.

‘So, I don’t think Mary would have been content to stick with that for all this time. I think she’d have wanted a different form of contact, and I think somewhere in the investigation we’ve already come across it, we just didn’t know it when we saw it.’

‘You think something in the investigation already tells us who this Mary is, and why she killed Connor and is obsessed with Eve?’

‘Yes. We have all the pieces; we just need to put them together to make the right picture.’

Nell thought for a moment. Carla’s theory might be right, but there was a nagging feeling she couldn’t get rid of, one that meant their investigation was about to get a lot more complicated.

‘Do you think Eve is in danger?’ she asked. Carla’s lack of surprise gave Nell her answer.

‘I’ve been thinking about that all night. I think we have to assume she is. If Mary is fixating on Eve, who knows how far she’ll go.’

Paul and Bremer were already in the office when Nell and Carla arrived. Carla hurried over to her computer and within seconds was immersed in every check possible to identify Mary. Bremer called Nell over and handed her a takeout coffee.

‘Thought you might need it. I certainly do.’

Nell didn’t even want to think what Bremer had done the previous evening to warrant a strong black, but she accepted the flat white offered to her.

‘Anything good come out of your visit to the social worker?’ he asked.

‘Well, I’m not sure it’s good news, but she was adamant there was no Eve Wilkes at the care home where Mary grew up.’

‘What does that mean?’ asked Paul.