‘They didn’t take the girls to wherever they were raped by car: MacSwain probably brought them there in his boat and afterwards he or someone else at the ritual took them by car and dumped them nearby.’ He snapped the mouthpiece back to his lips. ‘Patch me through to the Polizei Cuxhaven. I need to speak to Hauptkommissar Sülberg and I need to speak to him now.’

They were far out from the city by the time Sülberg’s voice came on the other end of the radio. Fabel explained that MacSwain was unaware he was being tracked and he was probably heading towards the general area where the other two had been abandoned.

‘Except this time,’ added Fabel, ‘he’s got a police officer who can identify him. He has no intention of letting her walk away from this, drugged or otherwise.’

‘I’ll get units out there right away,’ said Sülberg. ‘We’ll get into position and wait for your instructions.’

As soon as Sülberg was off the line, the co-pilot informed Fabel that Kassel had been in touch again. MacSwain had stopped. Somewhere just past Freiberg.

Fabel consulted his map. ‘The Aussendeich area,’ he said in a voice that the others could not hear above the thunder of the rotors.

Sunday 22 June, 00.10 a.m. Aussendeich, between Hamburg and Cuxhaven.

MacSwain’s boat was moored at an old abandoned wooden jetty that looked as if the wake of a passing boat would send it tumbling in pieces into the dark water. Kassel estimated that it had been there a good ten minutes before the WS23 had reached it. Time for MacSwain to have lugged Anna off the boat and out across the marshy fields that glistered coldly in the moonlight. Kassel and Gebhard had disembarked, weapons drawn, and slipped quietly into the bushes that fringed the field beyond. As they crouched in the scrub, Kassel could sense Gebhard’s electric excitement; this was the kind of action he had dreamed about. Kassel cast a look in his direction.

‘We take this easy, Gebhard, okay? I’ve radioed the Hamburg KriPo and they’ll take it from here. We just watch out that this guy doesn’t head back this way and try to escape on the boat.’

Gebhard nodded impatiently, like a teenager being denied permission to go to a party. Kassel scanned the field through his binoculars. The carelessly cast light of the moon was not bright, but Kassel could be pretty certain that there was no one there. MacSwain must have passed over to the other side. He lifted the binoculars the smallest degree and opened his horizon out by a hundred metres. There were two derelict buildings behind the far hedgerow: they looked like disused barns. He held them centre frame for a moment before recommencing his sweep back along the dark fringe of the field. Something snapped his focus back to the barns. A light. A faint, moving light inside the building to the left. Kassel slapped Gebhard twice on the shoulder with the back of his hand, then handed him the binoculars and pointed across to the barns.