Laura jabbed the eject button and almost shouted at the computer as it took an age for the drawer to open. Then she grabbed it and hobbled towards the door, going to the balcony to look out into the atrium. She was seeing if there was someone there she knew, or even the driver himself, but as she looked down, she saw only empty tables, the metal shutter on the canteen fastened down.

She headed for the stairs, taking two at a time, despite the complaints from her knee, and went towards the Incident Room, bursting through the door.

Carson was there, in conversation with the other detectives, their expressions pained, and Laura knew that they were talking about Rachel, how the case had come too close to the team.

‘I’ve got something,’ she said, and held up the disc. ‘It’s not Simon Abbott we’re looking for.’

‘What is it?’ Carson said, moving towards her.

‘Joe talked about the killer being Mr Invisible, about his frustration at being just an anonymous little man,’ she said. When Carson folded his arms, she continued, ‘What if he isn’t a police officer after all? What if he is just someone who works here, who floats around the station, ignored by all of us?’

Carson’s lips pursed as he thought about that. ‘What’s on there?’ and he pointed towards the disc.

‘I’ll show you,’ she said, and went to one of the computers and opened the disc drive. As the software loaded, she said, ‘It’s one of the drivers. Is there anyone more invisible? They get full access to everything, to deliver files and exhibits, but do we ever really notice them?’

Carson started to nod. ‘It would fit,’ he said.

‘So watch this,’ Laura said, and leaned forward to take control of the computer. She took the footage forward to where Rupert came into the police station.

As Carson watched Rupert, Laura said, ‘We thought yesterday that the killer knew that Rupert would recognise the methods he’d used, or else he knew that Rupert had been to the police station.’ Laura watched for Carson’s reaction, and when she noticed the slight widening of the eyes as the driver came into view, at the stutter in his walk, and the way he loitered by his van, Laura knew that Carson had seen what she had.

‘Does it look like him?’ he said, his lips tight, a flush to his cheeks.

Laura nodded. ‘Very much,’ and then she watched as Carson ran from the Incident Room.

The other detectives crowded round to look at the footage.

‘We know who he is now,’ she said, almost to herself. ‘We’ve got him.’

Suddenly, Carson came crashing through with one of the drivers, dressed in a blue jacket and trousers, a Lancashire Constabulary crest on his chest.

‘Who is that?’ Carson barked, pointing at the screen.

The driver looked scared, not used to having people shouting at him, but he took a deep breath as he realised that this wasn’t some minor enquiry.

‘It’s Peter Williams,’ he said.

Carson slapped him on the back and then told him to sit down. ‘Stay there,’ he said. ‘Don’t call anyone, don’t speak to anyone,’ and then Carson gestured for Laura to follow him. As she ran out of the room, she felt a certainty that they were almost there.

Chapter Sixty-Three

Carson drove quickly away from the station.

‘Do you think he’ll be expecting us?’ Laura said.

‘Murderers are always expecting us, because they know we don’t give up. He’ll have his story worked out. I just don’t want him getting rid of any evidence before we get there.’

Laura looked out of the window, her jaw set, her mind working its way through the different stages of guilt. She should have got a better view of him. And just a couple of hours earlier, could she have done more? She should have rushed him, but she hesitated and let him get away.

They had to cross town to get to where Williams lived, along terraced strips and up a long climb away from the town centre that took them towards the town’s hospital, which overlooked the green roll of the moors, an antidote to the glass and steel of the hospital building.

Laura’s phone rang. It was Archie, one of the detectives from the squad. ‘I’ve just spoken to the agency that recruits the drivers for us,’ he said. ‘He joined us six years ago. He said that he had been working as a motor cycle courier in London, and then a delivery driver, but both companies have since gone bust. His national insurance number was checked out, and he had no convictions, and so all the tests were passed.’

‘What about his personal history?’ Laura said.

‘That’s where it gets interesting,’ Archie said. ‘They’ve pulled his application form, and he said that he went to school in Stoke, but I’ve just tried to find it on the internet and it doesn’t seem to exist.’

‘So he’s got a made-up past,’ Laura said, catching Carson’s gaze as he drove.

‘At least some of it,’ Archie said. ‘He does have a clean driving licence, and so he is official.’

‘Except that if he is Shane Grix, he was supposed to have been murdered in a London alleyway,’ Laura said, and then she paused as she thought of something. ‘I’ll call you back, Archie. I’ll just give Sandy a ring.’

She went through her contacts list to find the number of her old London colleague. The phone rang out until she heard the London chirp. ‘I need another favour,’ she said.

‘Make it quick, darlin’,’ he replied. ‘I love a friendly voice, but it’s Saturday night and I’m in the boozer.’

‘Which one? The Green Man?’

‘Yes, why?’

‘Because you’re only across the road from the station. Could you go across and look in the Shane Grix murder file?’

There was a sigh. ‘Laura, the night’s just getting going. I’ve had too many drinks. Don’t make me do this.’

‘You’ll get the credit for solving that murder if you do,’ she said. ‘See if there is a list of Shane’s associates in the file.’

‘There is,’ he said. ‘I was looking at the file the other day, remember. We couldn’t track down most of them, because they were like him, homeless and drifting, keeping away from people like me.’

‘Look for a Peter Williams,’ she said.

Laura could hear his deliberations, but she knew that he would do what she asked, because for all the city boy charm he thought he had, he was a good copper at heart.

She smiled as he said, ‘Give me a few minutes, the file is still out. I’ll call you back.’

Carson glanced at Laura. ‘Are you thinking that the young man killed in the alleyway is really Peter Williams?’ he said.

‘We can guess that it probably isn’t Shane Grix,’ she said. ‘And so if it isn’t him, who else can it be? He must have stolen his identity when he killed him and started again.’

Carson frowned and drummed his fingers on the steering wheel. ‘Perhaps it’s even simpler than that.’

‘What do you mean?’

‘Maybe Williams was killed because of his identity, so that Grix could come back up here and do this.’

‘What, targeted murder?’

Carson nodded. ‘Why not? Perhaps Williams was his route back up north, where he could return and be anonymous, because Williams looked like him and so might pass for Shane once he was set on fire.’

Laura looked down when she felt her phone buzz in her hand. It was Sandy from London. She could feel the tension in the car as she listened to what Sandy had to say. When he’d finished, Laura thanked him and then turned to Carson. ‘It all fits,’ she said. ‘Peter Williams was one of the people on the list. They were seen together a few times before the body was found, sleeping in the same shelters. He was a couple of years older and had been in London a year longer. But he was invisible. Grew up in care, no family to speak of, and so he just headed south.’

‘And no one to look for him when he didn’t go home,’ Carson said.

‘That’s right,’ Laura said, nodding. ‘He wasn’t a suspect, just one of Shane’s friends, and so the police in London weren’t hunting him down. And like Sandy said, Shane was just another London homeless. They die all the time.’