Something else struck Fabel.

‘There are no files from Angelika Blüm’s apartment. And the missing video camera isn’t here either. He’s passed them on. He was told how to perform the murder and what to take from the scene.’ Werner appeared at his shoulder. With Maria and Werner now both behind him, he felt trapped in the tiny, airless space. He turned around and indicated the open space of the living area with a determined nod of his head. They all moved out.

‘It’s Anna, Chef,’ Werner’s face was clouded with worry. ‘It’s not good. She’s not in her apartment and she’s left her bag and cell phone behind.’

Saturday 21 June, 10.00 p.m. The Elbe near the Landungsbrücken, Hamburg.

The day that had been was trying to be remembered in a sky spun through with red and in the pleasant, lingering warmth of the night air. Franz Kassel lifted his cap and smoothed back the fine strands of sandy hair over his scalp. His shift was nearly at an end and he was looking forward to a cold beer. Or maybe a few. It had been a quiet shift and Franz had been able to savour what had attracted him to the Wasserschutzpolizei in the first place: hearing the delicate sounds of the water and the gentle creakings and ringings of boats at moor; watching the ever-changing light, passing beneath the vast, looming hulls of ships as he patrolled. Most of all, there was the different perspective it offered. Things always looked different from the water. You saw more. The Hamburg he saw every day was totally different from the one seen from dry land. He felt privileged to have this unique viewpoint.

He knew not everyone shared his sense of privilege: like Gebhard, the Polizeiobermeister who had the helm and was guiding the WS25 back towards the Landungsbrücken station. For Gebhard, the WSP was just a job; he had only been in the WSP for three years and already he talked incessantly to the other crew members about training and transfer to a land-based MEK.

Kassel watched as Gebhard steered towards the shore. Gebhard was competent, but he clearly lacked the feel for the water that Kassel believed was essential for any true river cop. It was something that lay within the natural sailor: the awareness of the river as a living entity. Gebhard, on the other hand, treated the Elbe as a water-filled autobahn on which he was no more than a traffic cop. Kassel left him to it and went to stand on the deck. The breeze cooled his face and he sighed the contented sigh of a man who has found his place and knows it. It was then that he spotted a boat he recognised exit from the moorings by the Überseebrücke. Kassel raised his binoculars. It was the Chris Craft 308 Cruiser they had been asked to watch the other night. He slipped quickly back into the cabin and ordered Gebhard to follow the cruiser, but at a safe distance.