There was no point in making an example of one or two. He had to cut a swathe through their ranks. He’d chosen his victims meticulously, plodding through reams of published papers in the journals of experimental psychology. He was only interested in those who might be regarded as the legitimate professional descendants of his persecutors – the Germans, of course, and their treacherous collaborators, the French, the Belgians, the Austrians and the Dutch. He’d ignored anyone who experimented on animals, looking instead for those evil bastards who not only used humans as the stepping stones for their own advancement, but who boasted of it in print. It was sickening, the way they detailed how they manipulated their subjects, twisting their minds and their behaviour. He’d been surprised that there weren’t more of them, but he supposed that not all of them were stupid enough to expose their own cruelties. It took a while, but finally he had a list of twenty names. He’d chosen to start with the ones who were based nearest the waterways, but if the need arose he could travel further afield later in his campaign.

Now, he had to be very, very careful. He had to plan every move with the precision of a military operation. And, so far, it had paid off handsomely.

He looked out of the porthole at the brown water surging past. Bremen would be next. The jar was ready and waiting.

Petra Becker was as cross as a cat whose mouse has been taken from it by a squeamish human. She’d had another frustrating day trying to prove a negative. They’d tracked down the man that Marlene Krebs was sleeping with, but he’d given them nothing useful. Marlene was a free agent, he’d shrugged. Yes, he’d heard she’d been seeing Danni, but he didn’t care so long as she practised safe sex, which she always did with him. You didn’t want to take chances with junkies, he’d added self-righteously.

Danni’s girlfriend had denied any knowledge of his supposed affair with Marlene, but they hadn’t lived together and she couldn’t say for sure where he’d been on the nights he hadn’t been with her.

Between them, Petra and the Shark had found three people who claimed to have known about the affair. The KriPo detectives were satisfied with that, but Petra wasn’t. One of the three had convictions for minor dealing, another worked in one of Radecki’s video stores. And the third owed so much to the local loan sharks that he’d have admitted to sleeping with the Chancellor if the price had been right. She didn’t believe any of them. But that was a long way from being able to disprove the story that Marlene still stuck so doggedly to.