Isaac turned from switching on the kettle and laughed wryly. ‘No. They’re complimentary copies, sent from the publisher. I was an advisor on a couple of the DCI Bartholomew books . . . How does peppermint tea grab you? I’m afraid I try to avoid caffeine.’

‘Sounds good. I should have avoided caffeine today – she says, four coffees later.’

There was a small tree of mint by a tiny high window. Isaac twisted the pot round and selected a couple of leaves.

‘My ex-partner is Stephen Linley, author of the DCI Bartholomew books,’ he said.

‘Oh.’

‘Oh, I’m gay, or oh, how odd to be with someone who writes crime thrillers?’

‘Oh, to neither.’

Isaac dropped the leaf into the cup and waited for the kettle to boil.

‘Actually, that is a bit odd, that you dated someone who writes crime thrillers,’ said Erika.

The kettle came to the boil and Isaac poured in water. ‘He based one of his forensic psychologists on me. Then killed the character off when our relationship ended.’

‘How?’

‘Gay bashed and dumped in the Thames.’

‘Sadly the pen is mightier than the sword,’ said Erika, taking the steaming cup.

Isaac took a seat at his desk and twirled the chair round to face her. ‘Ivy Norris had two types of semen inside her vagina. Her arms were bound, and she was strangled. Our attacker had not long departed. She’d been dead less than an hour.’

‘Anything from the DNA database?’

‘We’ve run both samples of semen, but nothing has come up.’

Erika nodded, and almost subconsciously looked at the back of her hand.

‘Is that a bite mark?’ asked Isaac.

‘Yes. It was Ivy’s grandson.’

‘Ivy’s blood work came back. She was a heroin addict and HIV positive. It’s feasible she passed it on to her grandson.’

‘When he bit me, he broke the skin,’ said Erika, sipping her tea.

‘Then I’d advise an HIV test.’ Isaac wrote a number on a piece of paper and handed it to her. ‘Here, it’s the drop-in clinic I use when I get tested. It’s fast, clean and anonymous. It can take up to six or nine months for the virus to show itself, so to speak. You’ll have to get tested again.’

‘Thank you.’

‘What are you going to do?’

‘I have to attend a formal hearing. Psychiatric evaluation. A medical, no doubt.’

‘If you are diagnosed with HIV . . .’

‘I’ll deal with that if it happens. Right now a fear of dying is well down my list.’

The album had finished and there was a comfortable silence in the room. Isaac looked at her, debating whether or not to say anything.

‘Don’t give up on this case,’ said Isaac.

‘I think the case has given up on me,’ said Erika.

‘I’ve been back through my records. There were three cases, autopsies I conducted, where the victims were Eastern European girls, all suspected of having been trafficked to the UK. All three were found raped and strangled, hands bound, dumped in water around London, hair pulled out, no clothes below the waist.’

‘What? When?’ asked Erika.

‘The first was March 2013, the second was November of that year and the third was February 2014. Just under a year ago.’

‘What? Why was this never flagged?’ asked Erika, sitting forward.

‘Circumstance often overrides putting the evidence together. Sadly the three girls were all prostitutes, whether they’d had a choice in the matter or not. They got lost amongst all the other killings; a prostitute is almost expected to lose her life. They were never linked, and the cases remain open.’

‘Dirt-poor Eastern European prostitute found strangled – oh well, shit happens. Young daughter of titled millionaire found strangled . . .’

‘Yes, it reads rather differently, doesn’t it?’ agreed Isaac.

‘Why didn’t you mention it before?’ asked Erika.

‘Something about Ivy’s death flagged it in my mind. Of course, Andrea differs from these because she hadn’t been raped. However. The other three girls were found in a state of decay, and they were sex workers. It’s possible they had been raped, but not at the same time as being killed. Ivy Norris was also a prostitute and was found with two types of semen. It’s possible that her killer didn’t rape her, either.’

‘Jesus!’ said Erika, standing up. ‘This is a major breakthrough. We now have four deaths linked with Andrea.’