Petra shrugged. ‘Not necessarily. The police forces in the different länder don’t have any formal liaison. There’s no central clearing house for information on crimes like murder, only for organized crime. We’re a big country and, frankly, most cops are too busy with their own workload to be bothered about what’s happening in other cities hundreds of miles away. And it’s not like America, where serial killing is almost part of the culture. Here, in Europe, we still don’t expect it to happen outside books and movies. No, Carol, the only way anybody’s going to make this link is if some detective like me picks up on it. And who’s going to connect the murder of a man in Heidelberg and a woman in Bremen, just because they were psychology lecturers?’

‘So you’re going to have to make it official now,’ Carol said.

‘Oh, I know,’ Petra said, blowing smoke down her nostrils. ‘It’s awkward, though. The first German case was never directly mine, and if I submit a report to Europol asking them to help co-ordinate an investigation, I will have to explain that Marijke broke her own duty of confidentiality when she told me about the Leiden case. And that is going to drop her right in the shit with her bosses.’

‘I see your point,’ Carol said thoughtfully. ‘Is there any way you could have read about the Leiden case and noticed similarities to the one you’d seen from Heidelberg, then connected those to Bremen?’

Petra shook her head. ‘There wasn’t much detail in the media. Not enough to mark it out as something that would have jogged my memory.’

‘I don’t suppose Marijke put out a search notice through Europol, to see if there were any other similar cases?’

‘I doubt it was even considered. Most cops, especially provincial cops, really don’t think of Europol as something that affects them. It’s not been up and running in an operational sense long enough to have become part of their automatic thought processes. I would think of it, of course, because my work is intelligence-based. But for someone like Marijke’s boss, it wouldn’t even cross his mind.’

‘Well, if you’re serious about wanting to protect Marijke, that might be the way to go. Get her to send a search request to The Hague, on the basis that this case has the hallmarks of the kind of killer who is likely to be a repeat offender and may be operating elsewhere in the EU. That would go out with the regular Europol bulletin, which I presume you see routinely?’

Petra nodded. ‘I think my team is one of the few departments that actually reads what comes out of Den Haag,’ she said wryly.

‘Perfect. Then you can weigh in with your recollection of the Heidelberg case. And bring in the Bremen case as a possibility.’