Smart woman, Carol thought. In your shoes, I’d be going crazy, not just feeling bothered. She nodded. ‘He’s not going to stop. You see this slipping away into some no-man’s-land of turf wars and arguments over the chain of command. Meanwhile, this bastard is free to carry on killing.’ As she saw recognition on Petra’s face, Carol realized with a sense of wonder that she was talking like Tony, stepping inside someone else’s head and articulating her fears.

‘You have put your finger on it precisely. This killer, he is a planner. He is good at what he does, and there is no reason for him to stop until he is caught. Meanwhile, the bureaucrats will be playing their games and the investigators will have their hands tied. It’s frustrating.’

‘It’s more than frustrating. It goes directly against the grain of what your instincts as a cop tell you needs to be done.’

‘Exactly. So, in my shoes, what would you do, Carol?’

The million-pound question, with only one possible answer. ‘Phone a friend,’ she said ironically. Petra frowned. Maybe Who Wants to be a Millionaire hadn’t travelled to Germany, Carol thought. ‘I wouldn’t let it go. I’d do everything I could to progress the investigation myself, and to hell with the official channels. And the first thing I’d do would be to get a profile.’

Petra’s face cleared. ‘Ah,’ she said. ‘I see. You would call Dr Hill?’

‘He’s the best. So yes, I’d call him and try to persuade him to come out of retirement and get back into the game.’

‘He has retired?’ Petra’s disappointment was palpable. ‘I didn’t think he was so old.’

It dawned on Carol that this whole thing had been one long preamble to try and secure Tony’s services for an unofficial serial-killer hunt. Sure, Petra had genuinely needed help with the mechanics of bringing it together in the public domain, but the real agenda was to enlist Carol and Tony on her team. Strangely, she didn’t feel at all used. She was genuinely amused, because she identified the strategy as one she would have cheerfully attempted herself. ‘He’s not old. But he’s not profiling any more. After the Vance case, he decided he didn’t want to be at the sharp end any longer.’

Petra looked dismayed. ‘Shit,’ she said. ‘I thought maybe …’ She shook her head, clearly angry with herself.