‘There’s more. The killer also scalped his victim. But not the head. The pubic hair.’

Carol could feel the hair on the back of her neck bristling erect. She knew enough about psychopaths to recognize the work of a disordered personality when she came up against it. ‘Well,’ she said, ‘it sounds as though it has some of the elements of a sexual homicide. Which means your man has quite possibly killed before and is likely to kill again.’

‘Both, I think. When Marijke told me about the case, it rang a distant bell at the back of my mind. And I found the murder of Dr Walter Neumann.’ Petra explained briefly what she’d discovered about the Heidelberg case. ‘So I began to think that we might be looking at a serial killer operating across national boundaries.’ She looked at Carol for a response.

‘A reasonable conclusion. From what you’ve told me, these crimes contain signature elements.’ She gave Petra a questioning glance, to see whether she needed to explain herself.

Petra nodded confidently. ‘OK, so I figured we had a big problem on our hands. As you know, there’s no formal operational liaison between national police forces in the EU, in spite of Europol and Interpol. Oh, we’re supposed to swap information and work jointly on transnational crime, and that sometimes works, like with what we’re doing against Radecki. But we both know how jealously cops guard their territory. Something as glamorous as a serial killer, nobody is going to want to mount an operation that might take the credit away from them. Getting them to share will be harder than pulling teeth.’

It smacked of cynicism, but Carol knew Petra was right. She also suspected that the greater glory of Petra Becker might be an element in the equation, but that wasn’t necessarily a bad thing. She knew herself she tended to be more committed to cases that would make her look good. It wasn’t something she was proud of, but she had to acknowledge it as a reality. ‘So you decided to sit on it and do some investigating of your own?’

Petra looked slightly uncomfortable. ‘I don’t know that I’d got as far as making a decision,’ she admitted. ‘It’s true that I wanted to be the one to break the news, and so I asked Marijke to send me the full details of her case. Because, if I was right, he started killing in Germany, which would give us some claim to be the primary investigators.’ Petra stopped abruptly and reached for her cigarettes. ‘But then, a couple of days ago, there was a third murder. I haven’t been able to get much detail yet, but it appears that a Dr Margarethe Schilling from Bremen University has also fallen victim to the same killer.’

‘Surely other people are going to pick up on it now?’ Carol said.