Rachel’s plan for Friday was the essence of compromise.

She would check out of the hotel, stow her luggage in the car and make a last detour to the apartment complex in an attempt to probe the undiscovered branches of the Rowe family tree. Just for her own satisfaction. And to do as Brickall had instructed; follow what her gut was telling her.

Then she would be content to admit that Rob was right, and that this was the end of the road, and she would hit the interstate to Washington DC in readiness for her flight the following evening. She would return to work and go through her DCI promotion assessments, having first feasted on the generous helping of humble pie which would no doubt be served up by both Brickall and Patten. There was a point at which a wild goose chase became less wild and more goose, and she had reached it.

She already knew from the helpful doorman that Harland left at 8.55 every morning, so Rachel reasoned that if she arrived soon after 9 a.m., apartment 714 would be empty but there would be enough commuter footfall through the lobby for her to blend in. She left her bag in the boot of the car and took just her phone and the spare keys to Harland’s apartment.

Sure enough, there were several people waiting to talk to the doorman about Amazon packages and dry-cleaning deliveries when she entered the building at 9.10, so nobody paid any attention as she called the elevator and went upstairs.

‘Hello?’

She called out as she unlocked the door, but as expected there was no reply. The apartment was as bland and orderly as the last time, and smelled of cleaning fluid and air freshener. In the kitchen, the breakfast dishes had been cleared and the counters wiped down. The dishwasher was sloshing quietly, and the tumble dryer hummed. Rachel went into Harland’s bedroom. The bed was made with starched blush-pink linen, smoothed and plumped like a hotel bed. There was nothing on the bedside tables, and only a hairbrush and a tube of hand cream on the dresser. The closet was half empty, with just a modest collection of elasticated waist trousers, tops and cardigans in size XL. A beige padded anorak hung alone in a corner, with a pair of sensible fur-lined boots on the floor below it, and a small black suitcase on the shelf above it. The en suite bathroom had white sanitary ware, counter and tiles. Off-white towels and bathrobe. Basic brands of shampoo and face cream, one toothbrush. Like Phoebe’s apartment, it was giving nothing away.

Like Phoebe’s apartment.

To her right as she came out of the bedroom there was a guest bathroom, opposite were the doors to the living room and kitchen, and to her left there was another door. The second bedroom.

She opened the door and stared.

The room was a mirror image of Harland’s in layout, but the antique iron bed was covered with a gaudy quilted bedspread in burgundy satin. The dressing table was crowded with make-up, brushes, hairspray and jewellery. Several pairs of high-heeled shoes lay discarded on the carpet and there were clothes draped on the bed. This was not Harland’s room. So whose was it?

Rachel sat down gingerly on the edge of the bed and examined the clothes. A green sequinned miniskirt, a sheer chiffon blouse, a strappy black dress with cut-out panels, all US size 6. The beauty products on the dresser would not have disgraced the collection of a professional make-up artist. There were highlighter powders and bronzers, palettes of shimmering eye shadow, primers, false lashes and hairspray; all premium brands. And a lipstick in a rose-gold tube. She twisted it up and stroked a slash of colour against her inner wrist. Orangey red.

Tangier Nights.

Her heart hammering in her chest, Rachel went into the walk-in closet. More clothes; sexy, glamorous size-6 clothes. Baskets full of plunging Victoria’s Secret bras and matching wispy knickers. Court shoes and strappy sandals and high-heeled boots neatly lined up against the wall. In the far corner of the top shelf there was a large black lacquer box. Rachel took it down and lifted off the lid, then stumbled back against the shelves, her head swimming with shock.

Inside there was a keyring in the shape of a metal P. P for Phoebe.

She waited for the pounding in her chest to subside a little and looked inside the box again. A Padres baseball cap. A framed photo of Melissa Downey and Clayton Hill. A pair of burgundy Valentino T-bar courts.

There it was: all of it. The key was the spare that Matt Wyburgh had given to Phoebe, the cap – from Tiffany’s local team – worn by the killer on CCTV, a photo from Melissa Downey’s apartment and the shoes. Rachel took them out and examined them. Size 9. They almost certainly belonged to Talia Schull in Boston, she of the lucky escape.

Here was her incontrovertible proof. Harland was linked to whoever carried out the CasaMia killings. But she wasn’t operating alone, and the size-6 accomplice couldn’t possibly be her sister Kaydance. It wasn’t Rainey, or Brianna or Melody. So who the hell was it?

Rachel waited for her breathing to calm and her detective instincts to kick in. She pulled out her phone from her trouser pocket and took photos of the souvenirs, and the lipstick, then placed the box back on the shelf. Something propelled her back to Harland’s closet, only this time she took down the black suitcase and opened it. Inside were bottles of Citranox, Tevlar suits, latex gloves.

Slamming the case shut, she dialled Rob’s number, fingers still trembling.

‘I promise I’ll pick up next time…’

He did not pick up.

She dialled again, and again, and again; the last time leaving a message demanding he call her urgently. Then she went into the living room, where she remembered seeing a laptop on the desk. It was password protected, naturally.

She phoned Mike Perez, and he answered on the second ring.

‘It’s not even the weekend yet, and you’re already—’

She cut across him. ‘Mike, this is urgent. I’m at Harland Rowe’s apartment.’ She was speaking like a speeded-up recording, trying not to waste time. ‘And I’ve finally found the evidence. Real, not circumstantial, and—’

It was Perez’s turn to interrupt.

‘Slow down.’

‘I’ll explain later, but for now can you tell me how to get past the password protection on a laptop? Quickly.’

He sensed the urgency in her voice and dropped the playful tone. ‘Okay, press Control R or Command R and wait for it to reboot in recovery mode.’

She watched the screen go grey and a loading bar appear. ‘Okay, now what?’

‘Go into Utilities, select Terminal and then type in “resetpassword” – all one word. Got that?’

Rachel’s fingers felt thick and sausage-like as she typed incorrectly then tried again. ‘Now?’

‘That should pull up a password reset box. Yes?’

‘Yep.’

‘Okay, you just need to select the user account you want to get into, then the “Enter new password” option. Leave it blank and press enter, and you should be in.’

There was only one user account, helpfully called HRowe. Rachel did as instructed, and there she was on Harland’s desktop.

‘Did that work?’ Perez was asking her.

‘Yes, it did. Thanks, I really owe you one.’

‘I think we’re up to at least three now… what’s the address there, so I can—’

‘Gotta go.’ Rachel hung up and shoved her phone back in her pocket, already pulling up Harland’s browser history on the laptop. The most recent hit was some online shopping, then Facebook and Instagram hits. Lots of them. She scanned further down the list. There it was. CasaMia.com.

Rachel went straight to account avatar in the top right-hand corner.

Welcome, Linda!

Harland was currently logged on to the site as someone called Linda Ruffner. The account profile photo was of a girl who was young and pretty. A girl who was not Harland, and whose image was undoubtedly pilfered from her cloud storage. Linda Ruffner had not been on any trips yet, but she had saved several properties as favourites, accessed by clicking on a red heart icon. Rachel paused, and listened. It felt as though hours had passed, but it was still only ten o’clock. While the list was loading, she used the guest cloakroom, being careful not to disturb anything. Then she returned to Harland’s laptop to scrutinise her choices, although she already knew what she would find.

There was a shabby chic apartment in Austin, Texas, belonging to Jacqui Garcia. Jacqui looked a lot like Melissa Downey, and listed her hobbies as ‘Horseback riding, yoga and hanging out with my awesome bf’. Rachel stared, breathing deeply, before moving on to the next favourite. Laine Zabreski had a charming Victorian conversion in Charleston, South Carolina and if you squinted slightly could have been the girl in the Lovely Locks commercial. Then there was Amy Burns, a former high-school track star in Duluth, Minnesota and Kristin Coley, who had a beachside condo in Long Beach, California and was ‘a self-confessed surf freak’. All conforming to the favoured personality profile. Rachel felt sick. There was still no reply from Rob’s number. She took screengrabs of all the saved favourites, plus Linda’s profile, then clicked the message inbox icon.

Four messages from the CasaMia customer service department. They all contained identical wording.

And so on. So the CasaMia security firewall on the potential targets was working, which was reassuring. Rachel used her phone to forward the screen grabs to Paulie anyway, under the subject ‘Suspect still active’, then returned to Harland’s browser history.

The social media pages searched through belonged to the hosts on CasaMia: Jacqui Garcia, Laine Zabreski, Amy Burns and Kristin Coley. Rachel found what she expected to find; the curated evidence of happy, privileged lives. Parties, family occasions, handsome boyfriends, laughing friends. Her mind went back to the conversation she had had with Rob when they were in North Carolina.

What are the characteristics that define the targeted group?

Pretty. Spoilt. Popular. Self-absorbed. Entitled.

And there it was: the abundant evidence of those qualities, displayed in their online lives for the world to see. Curated and edited to seem aspirational. These women had not done anything to Harland and her accomplice, they just were a certain way.

Rachel logged out and shut down the laptop. It was time to move. Now. She would drive straight to Rob’s office and lay out the evidence for him. They had the brains of the operation in Harland Rowe, all they need was to crack the identity of whoever was assisting her. The lookalike who was entering the homes of the victims she selected and killing them for her. The occupant of bedroom number two.

Rachel went back in there now for one last look around and to take the P keyring as corroborating evidence. As she slipped it into her back pocket, her heart leapt against her sternum and she darted into the hallway and shut the bedroom door.

The sound was unmistakeable. A key turning in the apartment’s front door.