Schwartz knew that this fundamentally insurmountable problem was the reason he’d been the one chosen for this operation. Since the death of his family he’d been regarded in police circles as a ticking time bomb. A thirty-eight-year-old undercover investigator, marching briskly towards retirement age in his profession, and lacking the key thing that kept him and his team alive in emergencies: a sense of fear.

He’d been examined four times by police psychologists. And four times they’d come to the conclusion that he hadn’t got over his wife’s suicide – let alone the fact that she’d killed their son beforehand. Four times they recommended early retirement, because a man who no longer saw any point in his life would take irresponsible risks in the line of duty.

They’d been right four times.

And yet here he was again in the police vehicle, not only because he was the best for the job, but chiefly because no one else would voluntarily have HIV antibodies injected into their bloodstream to manipulate the instant test. Although a special sterilisation process purified the blood serum of pathogens that triggered AIDS, the team doctor refused to declare it one hundred per cent safe, which is why as soon as this was over Schwartz had to start a four-week course of drug therapy, known as post-exposure prophylaxis, or PEP for short. Something he’d already been through once before when a junkie in Hasenheide Park jammed a bloody needle into his neck. The instruction leaflet that came with the ‘after pills’, which had to be taken two hours at the latest after the danger of infection, noted that the possible side effects were headache, diarrhoea and vomiting. Schwartz seemed to be more sensitive than other subjects. He may not have been sick or spent longer on the loo than normal, but terrible migraines had driven him to the verge of passing out, even beyond sometimes.

‘I’ve got to get cracking,’ he said to Kramer while eyeing the monitor. Nobody had entered the house for ten minutes.

They’d counted seven guests: five men, two women. All had come by taxi. Handy, if you wanted to avoid your registration number being taken down.

‘What if Pryga has made contingency plans and found a replacement for me, just in case I pull out?’ Schwartz asked. In all likelihood the guests were healthy. Certainly not mentally, but physically so. But of course they couldn’t know for certain.

Kramer shook his head. ‘There aren’t so many infected paedophiles prepared to do such a thing. You know how long Pryga had to look for Jensen?’

Yes, he did.

All the same. The risk was too great.