‘Because I just need to look into this. They’ve made their minds up, obviously. It’s easier to charge Isaac… Ends it all neatly, case solved.’

‘You don’t think he did it?’

Erika looked at Peterson. ‘No, I don’t. I just need to check this out myself. It’s a long shot, but if I phone it in, it’ll get shoved to the bottom of the pile and it might be too late before anyone gets to it. You okay with this?’

He shrugged and grinned. ‘As you said on the phone, boss. It’s just a day out by the sea.’

‘Thanks.’

Erika thought how things had changed. She was now on the outside. She started to fill Peterson in on what she had discovered and how she’d like to proceed.

Ninety minutes later they came off the dual carriageway and approached Worthing via a complex and unattractive one-way system. When they arrived in the town, though, it looked picturesque. It was an old seaside town, which in the height of the summer looked more sumptuous than crumbling. Erika followed the road along the promenade. The beach was crowded with people sunbathing and sitting on old-style deckchairs. It was lined with terraced houses, flats and an eclectic selection of shops. She parked on the seafront and they stepped out onto the busy promenade, where people sauntered along, eating ice creams and enjoying the sun.

‘How should we play this?’ asked Peterson, joining her at the parking meter by the kerb.

‘We have no authority to be here, but he doesn’t know that,’ said Erika, feeding coins into the machine. ‘I’m hoping the element of surprise will work in our favour.’

She took the ticket from the machine and they locked up the car. The address they were looking for was further down the seafront, where the souvenir shops and tearooms thinned out. The terraced houses here were much more run-down and had been turned into flats and bedsits.

‘Here, this is it,’ said Erika, as they came to a large five-storey house with a small concreted-over front garden which contained five black wheelie bins with flat numbers painted in white on the lids. The windows were all open and music blared out from the top floor.

‘I can smell weed,’ said Peterson, stopping to sniff the air.

‘We’re not here about weed,’ said Erika. ‘Just remember that.’

They went up the steps and Erika rang the bell for the ground-floor flat. They waited as the music ceased for a second, then Nirvana’s ‘Smells Like Teen Spirit’ began to play.

The lights were all blazing in the downstairs window, which looked out over the bins and was half-obscured by hanging clothes. Erika rang the bell again and through the frosted glass in the door she saw a large, dark bulk move from the shadows. The door opened an inch, then stopped. Moments later there was a whirring noise and the door was slowly pulled open.

The dark bulk she had seen was an enormous motorised wheelchair, which had heavy-duty wheels and oxygen tanks strapped to the back. A concertina mechanism whirred and elevated the seat, in which a tiny man sat. He had small, plump features, thick glasses and wisps of mousy hair clinging to his bald head. He wore an oxygen tube under his nose. His body was compact – they could see he suffered from dwarfism – and his even tinier pair of emaciated legs, which just reached the edge of the seat, contrasted his small body. One of his arms was tucked into the side of the seat and the other was holding the piece of string he had used to open the front door. He let the string go, grabbed the remote control beside his chair and moved forward, blocking the threshold.

‘Are you Keith Hardy?’ asked Erika.

‘Yes,’ he said, his eyes darting between them. He spoke with a higher-pitched voice.

Erika and Peterson held out their IDs.

‘I’m DCI Erika Foster and this is my colleague, DI Peterson. Could we have a word?’

‘About what?’

Erika looked at Peterson. ‘We’d prefer to discuss this inside.’

‘Well, you’re not coming in.’

‘We won’t take up much of your time, Mr Hardy,’ said Erika.

‘You won’t take up any.’

‘Mr Hardy…’ started Peterson.

‘You got a warrant?’

‘No.’

‘Then go away and get one,’ the man said. He reached out and grabbed for the string attached to the inside lock. Erika leaned over and plucked it from his grasp.

‘Mr Hardy, we’re investigating a triple murder. The killer used suicide bags… We’ve accessed your bank accounts and we see you’ve bought five of these, and yet you’re still alive. It’s just a case of clearing up any misunderstanding.’