‘We’ve been trawling through all the CCTV footage,’ he said. ‘Not the car park cameras, the town centre ones. Remember we eliminated all the vehicles in the multi-storey itself? And we reckoned our man must have taken Sandra Birley out on to the street…’

‘Yes?’

‘Well, we got a possible sighting at the corner of Hardwick Lane and New Street.’

‘Let’s see it.’

They played back the tape for her. It had been recorded by a camera high above New Street, close to the traffic lights at the start of the pedestrianized section of Clappergate. Seven forty-five. It was pretty much dark, of course, but the street lighting was on and the quality of the image was surprisingly good. At first, there seemed to be no one in the street, only the brake lights of a car moving away from the camera position.

Then a dark shape appeared from the corner of Hardwick Lane. It seemed to be one person. But a second later, Fry realized there were two people, one much heavier and taller than the other. They were unnaturally close together, the larger with his arm around the smaller.

‘Is that Sandra Birley on the left, do you think?’

‘We estimate she’s about the right height to fit the description,’ said one of the operators. ‘Dark-haired, too. And she’s wearing a skirt, as you’ll see in a moment.’

The smaller figure seemed to stumble, or try to pull away. As they separated, it became clear for the first time that she was a woman, wearing a dark skirt with a hem just above knee length. Then she was pulled back towards the tall man, seemed to stumble again, but regained her footing.

‘There’s no indication that he’s threatening her with a weapon,’ said Fry.

‘No, sorry.’

‘Maybe he didn’t need to,’ said Murfin. ‘He’s twice her size at least.’

‘Why didn’t she scream, though? There must have been people within earshot.’

‘OK, he could be holding a knife close to her body. We wouldn’t see it from this angle, nor would any passers-by in the street. She wouldn’t dare scream with a knife in her ribs.’

‘That’s possible.’

The couple made slow progress up the street. This was no quick getaway. At one point, the woman seemed to turn towards the man and speak to him. No, she was arguing with him, trying to turn back the way she’d come. He shook his head, said something, pulled her roughly along with him again. This time, the violence was more overt.

‘We eliminated the Sheffield man, didn’t we?’ said Fry, watching the jerky footage.

‘Yes. Dad’s Army checked him out,’ said Murfin.

‘Who?’

‘Oh, the temporary CID support staff.’

‘Right.’

‘And remember, his car was parked in the multi-storey. This one is in New Street, look –’