‘Are we going to get the husband to make an appeal, sir?’ asked Cooper, raising his hand. Fry nodded reluctantly to herself. At least that was one tactic they could use without committing themselves to anything.

‘We think it’s too early yet,’ said Hitchens. ‘Besides, he isn’t in any condition at the moment. I spoke to the family liaison officer first thing this morning, and it seems Mr Birley’s emotional state has deteriorated considerably since yesterday.’

Then it turned out that the two retired DCs had been working an early shift, too. They’d already been through the CCTV footage from the Clappergate multi-storey. That wasn’t anybody’s favourite job. Feelings in the room began to warm towards them.

‘First of all, we’ve eliminated the owners of the other two vehicles that were left in the car park overnight,’ said the one with the black-and-white tie. ‘The first bloke had drunk too much in the pub and sensibly decided to get a taxi. He turned up to get his car next morning, so we got a statement from him. He didn’t see anything. But how would he, when he was in the pub at the time?’

‘OK,’ said Hitchens. ‘And the other one?’

‘Even more innocent. He works in the IT department of a company with offices in Buxton Road. That afternoon, he dropped a computer monitor on his foot and broke two toes. He was in A & E at the relevant time. His girlfriend turned up to collect the car.’

‘They never really looked like contenders anyway. Why would Sandra Birley’s attacker leave his own vehicle in the car park as well as hers?’

‘Exactly, sir. But we had to eliminate them. We’ve also been through every bit of tape from the functioning cameras, and we’ve managed to trace all the vehicles that left the car park later that night – in other words, after Mrs Birley was abducted. There were only four of them, because the place was practically empty. In fact, we’ve matched all but one of those vehicles to CCTV footage of the owners returning to their cars. Two were lone males, and there was one couple – but older, in their early sixties. It’s clear from the tape that the woman isn’t Sandra Birley. She’s the wrong age, wrong height, wrong clothes, everything. All of these people have been spoken to, and they seem to be genuine.’

‘And none of them saw anything suspicious?’ asked Fry.

‘That’s right, Sergeant.’

Fry sighed. That was the trouble with law-abiding members of the public – they never saw anything. She’d lost count of the number of times she’d attended a serious incident, only to be met by members of the public with helpful smiles and short-term memories.

‘If my maths are correct, there was one more vehicle.’

‘Unfortunately, the fourth vehicle seems to have been parked on Level 2.’

‘Where there’s a non-functioning camera?’

‘You’ve got it, Sarge. We do have footage of the vehicle exiting the car park at the barrier. It’s a blue Saab. There appears to be a male driving, no one visible in the passenger seat.’