She works her way along until she reaches 1990. Most of the files contain several different cases. She chooses one at random. Drunk driving, July. Breaking and entering, also July. The typewritten documents have gone yellow with age. She moves on to the next file. Domestic abuse, driving without due care and attention, both August 1990. The remaining three cases are of a similar calibre – not what she’s looking for. Even before she takes out the next file, she knows it’s the right one. According to the information on the spine, it contains only one case. It is lighter than she’d expected.

On the night of 28 August 1990 car 3495 was called to Mörkaby quarry to investigate a death.

Bingo! She carries on reading as her pulse rate increases.

On arrival the body of Simon Vidje was found floating on his back in the water. There were four witnesses in the immediate vicinity of the scene.

Alexander Morell, Bruno Sordi, Marie Andersson and Carina Pedersen, all nineteen years old and all friends of the deceased.

Carina, not Catrin, that was the name of the fourth person – or fifth, depending on your point of view. She is about to read on when the light goes out and the room is plunged into darkness. The motion sensor is over by the door and she is hidden by the shelves, which means the wretched thing thought the room was empty. She tucks the file under her arm and feels her way along the shelves with her free hand. An unexpected noise makes her stop dead: the squeak of a rubber sole on a vinyl floor. She stays where she is, listening.

A key turns, the door opens and the light comes on, bathing her in a harsh white glow.

‘What are you doing here?’ Jens Friberg asks.

‘Looking for some old cases.’ She tries to sound nonchalant. ‘Actually, it’s a good job you turned up.’ She feels a stammer coming, waits, then goes on. ‘The light had just gone out and I was trying to find my way to the door.’ She gives him her best smile, which has no effect whatsoever.

‘Which cases, if you don’t mind my asking?’ His eyes move to the file under her arm, then to the shelf behind her. The dates are clearly visible. She sees his brain trying to make sense of the details, then his eyes narrow as the penny drops and he realises what she is doing. She presses the file a little tighter to her side and takes a deep breath.

‘Thanks for your help, Jens. I’m heading back up to . . .’ She nods in the direction of the doorway behind him.

He makes no attempt to move. Instead, he simply stares at her. She meets his gaze, does her best not to show any sign of hesitation. Takes a step forward; the distance between them is now considerably less than comfortable.