‘I watched the tapes, trying to determine whether everyone who went in between ten-thirty and eleven, also came back out. Everyone is accounted for. Except this guy right here.’ He pointed to the screen. ‘He entered the school premises at ten forty-nine p.m.’

‘And he didn’t come back out?’

‘Well, if he did, he certainly didn’t come out the same way he came in. I’ve triple-checked the tapes. He’s not on any of them.’

The man in the photo had his back to the camera. There was something familiar about him, but Yngve couldn’t quite determine what. He was slouching somewhat. Skinny. Brown hair.

‘A parent, maybe?’ Weedon offered. He replayed the video tape, frame by frame. On screen the man placed his right hand on the door handle and pulled it towards himself. Then he entered the school.

‘Can you zoom in on his hand, please?’ Yngve pointed to the screen again.

Weedon nodded, clicking and moving with his mouse. He then reversed the tape and did as Yngve had asked. The image was grainy, but the man’s fingers were still visible.

‘No ring,’ Yngve said.

An image appeared before Yngve’s mind’s eye. Frode Lindgren, squeezing his ball of socks. Yngve hadn’t noticed it then, but now, when he came to think of it, he was almost a hundred percent sure that Frode hadn’t been wearing his wedding ring that day.

Yngve studied the picture more closely. He couldn’t really say that he knew Frode Lindgren well, but there could be some resemblance, at least in height and posture.

‘Print out the best image you can find,’ Yngve said to Weedon. ‘Make eight to ten copies to begin with, and then we’ll bring everybody who was still at school around that time in for questioning again.’

Weedon began searching through the recording straightaway.

‘Let’s see if we can identify those girls as well,’ Yngve continued and pointed to the screen, even though they weren’t on it anymore. ‘Find out if they noticed the guy as he was passing. Maybe one of them knows who it is.’

‘I’ll see if I can pull a picture of his face from a reflection in the window as well,’ Weedon said.

‘I’d be very pleased if you can,’ Yngve said. ‘Excellent work, gentlemen.’

Back at his desk he called Therese Kyrkjebø over and quickly briefed her on what they’d found on the CCTV recordings.

‘I want you to try and get hold of some of Børre Halvorsen’s friends,’ he said. ‘We need to know what he was doing the last days of his life. Whether he was having trouble with anyone – conflicts his mother wasn’t aware of.’

‘She wasn’t aware of a whole lot of things.’