‘You’re confirming there is something going down? Something that takes it away from us?’ Now her blood was up and she didn’t care that she was overstepping the mark. Her eyes were narrowed and there were patches of colour on her cheeks and neck.

‘Don’t push me,’ Plesch said, getting to her feet. ‘Just go out there and do your job. We need to talk about this some more, but not now. Listen to me, Petra. We’ve worked together long enough for you to understand that there are times when you have to trust me. This is not a good time for you to rock the boat. Don’t go down the high-risk road. It’s not necessary and it’s not desirable.’ She forced a smile. ‘That’s an order, by the way. You don’t expose the child.’

Petra had walked out fuming, her hands clenched into fists at her side. Only later, when her initial anger had subsided, had she analysed what Plesch had said to her. She had verified, albeit indirectly, that something major was going to change in the Radecki investigation. But she seemed to be suggesting that there would be a role for Petra if she kept her nose clean. It was a long way from a promise, but it made her feel slightly less raw about Plesch’s dismissal of her plan.

She slouched in her chair and logged on to her internal e-mail. She wasn’t expecting anything interesting, but it was better than staring at the wall. She scanned the short list of new mail. The only thing that piqued her attention was a reply to her request for information from the police in Heidelberg. Given the way things had been panning out for her over the past couple of days, she refused to allow herself to feel eager, but she opened the e-mail anyway. Her eyes flicked down the screen, taking in the key details: Walter Neumann, 47. Lecturer in psychology at the Ruperto Carola University of Heidelberg.

Petra felt a blip on her mental radar. Another academic, another psychologist. This was promising. She scrolled on down. Three weeks previously, he’d been found by a student in his apartment near the Altstadt campus. His computer had been smashed to the floor and he’d been spread-eagled on his back across his desk. The details were identical to the information Marijke had given her about de Groot’s murder in Leiden, right down to the cause of death – drowning – and the cutting away of the pubic hair and the skin attaching it to the body.