‘Corporate Crime say they’re screwed if the Staatsanwaltschaft won’t accept that they’ve established reasonable grounds for seizure,’ said Werner. ‘And without the paperwork to prove wrongdoing they can’t bring a case.’

Fabel’s face hardened and he snatched up the handset of his phone and dialled the cell phone number the Ukrainian had given him.

‘I was not expecting to hear from you so soon, Herr Fabel,’ said Vitrenko senior, in his perfect but accented German.

Fabel explained the situation with the Staatsanwaltschaft state prosecution service. ‘I need something, anything, concrete that gives us grounds for detaining the Eitels longer and getting our hands on their files. The Eitels are our only potential link to your son’s organisation.’

There was a silence at the other end of the phone. Then the Ukrainian said: ‘I don’t know if I can help you. There is certainly nothing I can give you right now. But meet me tonight, say eight o’clock, in the warehouse in the Speicherstadt.’

The hard resolve on Fabel’s face remained undiluted when he came off the phone. ‘Werner, go get Maria. We’re going to visit the BAO.’

Maria talked as the trio walked briskly along the corridor that led from the elevator to Volker’s office. She handed Fabel three or four pieces of paper stapled together.

‘I checked into Vitrenko. This is as close to a background as we’re likely to get. From what I can gather the Berkut unit is being built into a serious counter-terrorist and anti-organised-crime outfit, although its primary function has until now been basically that of a riot squad. As an operational unit it is similar to GSG9 here in the Bundesrepublik. They are clearly very highly trained. I contacted their headquarters in Kiev – they were cooperative but not overly forthcoming about Vitrenko. It would appear that he was one of their top experts on Islamic terrorism, mainly because of his time in Afghanistan and Chechnya. All I got from them was this résumé of Vitrenko’s career. Buried in amongst it all was this …’ Maria flipped over a couple of the pages Fabel was holding. There was a sheet headed with what Fabel guessed was the crest of the Ukrainian Interior Ministry above a page of Cyrillic text. The next page was the translation into German. ‘Look at this: two weeks training at a serial-offenders profiling unit in Odessa.’

Fabel came to a halt. ‘And you said my Europol paper on the Helmut Schmied killings was circulated in the Ukraine?’

‘Exactly. I’ve still to get a reply, but I’ll bet a month’s salary that it featured or was available as part of the course.’

Fabel felt the hunger that comes to the hunter when close to his quarry. ‘That’s why we’ve been dealing with a classic textbook case of psychotic serial murder; because it’s all based on textbook cases. And he chose me because he happened to read a paper I had published on serial offending.’

Werner gave a bitter laugh. ‘So he thought he could pull all of your strings and have you look in the wrong direction.’