‘So the holiday’s going well?’ said Moss, moving a couple of grey folders and perching the pizza box on the end of the coffee table.

‘I got another call.’

‘From the Night Stalker?’

‘Yeah.’

‘What did she say?’

‘She phoned to screw with me. She told me she wasn’t finished yet.’

‘Did they get a trace?’

‘Yes, Crane called me. He’s been reassigned to the case, at Sparks’ request. They traced it to a phone box in West London. Again, no CCTV… He couldn’t tell me much more… How is she not slipping up? How? I’ve been printing everything off from the case. It helps, having hard copies. I’ve been going back through everything.’

Erika handed Moss a plate and a napkin. She opened the box and steam rose from the thin crust pizza, which was cooked to perfection. As they began to eat, Erika relayed what had happened when she visited Isaac and detailed how she was revisiting all the evidence after the phone call.

‘I just feel we never had a real crack at working her out, the Night Stalker. Like the card she sent me.’ Erika handed Moss a printout of the scanned card. ‘Why did she choose that poem?’

‘She’s a vicious serial-killing bitch. Why should she be any more imaginative than the rest of us?’ said Moss. ‘As a poem, “Do Not Stand At My Grave And Weep” is not hard to seek out. It’s the go-to poem for funerals. It’s like books: we all scan the bestseller lists, we see what reviewers are telling us to read and we buy them to make ourselves feel clever. I was one of the many millions who read half of The Goldfinch.’

‘That’s what the Night Stalker said on the phone.’

‘That she only read half of The Goldfinch?’

Erika shot Moss a glare.

‘Sorry, boss, just trying to lighten the mood…’

‘She said on the phone that she wasn’t clever,’ said Erika.

‘But she is clever. Or bloody lucky. Three bodies so far and virtually no evidence. She slips in and out unseen,’ replied Moss, taking a bite of pizza.

Erika shook her head. ‘Why go to all the effort of finding my flat, breaking in and leaving a card? And she signed it “The Night Stalker”.’

‘Maybe she thinks she has a new friend or ally in you, boss.’

‘Then why not sign it with her real name, if she’s that confident? Serial killers often hate the names they’re given in the press. They think it erodes how they are seen by people. They think what they’re doing is serious: a noble deed, or series of deeds; a service to society.’

‘Maybe she just wants to screw with your head,’ said Moss.

‘I’ve also gone back over the victims, trying to see if they had anything in common, but they’re vastly different people. The only thing they have in common is that they are male, and that they were killed in exactly the same way – except that Stephen had his head smashed in as well. I also looked back over the names of people who bought these suicide bags online.’

‘I’ve been through the names, too. So many of the London-based women who bought them are now dead,’ said Moss.

‘There’s something that Isaac said when I saw him this morning. When he discovered Stephen’s body, he’d let himself into the flat with a key. The door was closed and locked. No forced entry. The flat is on the second floor, with no balcony or other doors.’

‘So the Night Stalker had a key?’ asked Moss.

‘Yes. I got the report from the crime scene. The lock had been bumped. It was damaged inside from someone using a bump key.’

‘They’re pretty common in burglaries, and you can buy them online for nothing these days,’ said Moss.

‘Exactly. And there’s one person on the list of people who bought suicide bags online who also bought a bump key online,’ said Erika.

‘Really?’

‘Yeah, when we followed up on the names, we went as far as accessing bank accounts and financial transactions. This person bought a suicide bag three years ago, and then in the last three months has bought five more. Who needs five? They also bought the bump key online three months ago.’

‘Bloody hell! Why didn’t we follow it up?’ asked Moss.

‘It must have been overlooked – we weren’t looking for a bump key, and we were focusing on women. This person is a thirty-five-year-old male. He’s been wheelchair-bound since childhood. He lives in Worthing, on the south coast, not far from London.’