Pip exited on to the home screen and opened the messages app. She clicked on the Andie tab, feeling like a time-hopping trespasser.

Sal had sent two texts to Andie after she disappeared. The first on the Sunday morning: andie just come home everyones worried. And on Monday afternoon: please just ring someone so we know youre safe.

The message preceding them was sent on the Friday she went missing. At 9:01 p.m. Sal texted her: im not talking to you till youve stopped.

Pip showed Ravi the message she’d just read. ‘He said that just after ignoring her call that night. Do you know what they could have been fighting about? What did Sal want Andie to stop?’

‘No idea.’

‘Can I just type this out in my research?’ she said, reaching over him for her laptop. She parked herself on her bed and typed out the text, grammar mistakes and all.

‘Now you need to look at the last text he sent my dad,’ Ravi said. ‘The one they said is his confession.’

Pip flicked over to it. At 10:17 a.m. on his final Tuesday morning, Sal said to his father: it was me. i did it. i’m so sorry. Pip’s eyes flicked over it several times, picking up a little more each read through. The pixelated building blocks of each letter were a riddle, the kind you could only solve if you stopped looking and started seeing.

‘You see it too, don’t you?’ Ravi was watching her.

‘The grammar?’ Pip said, looking for the agreement in Ravi’s eyes.

‘Sal was the cleverest person I knew,’ he said, ‘but he texted like an illiterate. Always in a rush, no punctuation, no capital letters.’

‘He must have had autocorrect turned off,’ Pip said. ‘And yet, in this last text, we have three full stops and an apostrophe. Even though it’s all in lower case.’

‘And what does that make you think?’ asked Ravi.

‘My mind doesn’t make small jumps, Ravi,’ she said. ‘Mine takes Everest-sized leaps. It makes me think that someone else wrote that text. Someone who added in the punctuation themselves because that’s how they were used to writing in texts. Maybe they checked quickly and thought it looked enough like Sal because it was all lower case.’

‘That’s what I thought too, when we first got it back. The police just sent me away. My parents didn’t want to hear it either,’ he sighed. ‘I think they’re terrified of false hope. I am too, if I’m honest.’

Pip scoured through the rest of the phone. Sal hadn’t taken any photos on the night in question, and none since Andie disappeared. She checked in the deleted folder to be sure. The reminders were all about essays he had to hand in, and one about buying his mum’s birthday present.

‘There’s something interesting in the notes,’ Ravi said, rolling over on the chair and opening the app for her.

The notes were all quite old: Sal’s home Wi-Fi password, a listed abs workout, a page of work experience placements he could apply to. But there was just one later note, written on Wednesday 18th April 2012. Pip clicked into it. There was one thing typed on the page: R009 KKJ.

‘Car number plate, right?’ Ravi said.

‘Looks it. He wrote that down in his notes two days before Andie went missing. Do you recognize it?’

Ravi shook his head. ‘I tried to Google it, see if I could find the owner, but no luck.’

Pip typed it up in her log anyway, and the exact time the note was last edited.

‘That’s everything,’ Ravi said, ‘that’s all I could find.’

Pip gave the phone one last wistful look before handing it back.

‘You seem disappointed,’ he said.

‘I just hoped there’d be something more substantial we could chase up on. Inconsistent grammar and lots of phone calls to Andie certainly make him appear innocent, but they don’t actually open any leads to pursue.’

‘Not yet,’ he said, ‘but you needed to see it. Have you got anything to show me?’

Pip paused. Yes, she did, but one of those things was Naomi’s possible involvement. Her protective instinct flared up, grabbing hold of her tongue. But if they were going to be partners, they had to be all in. She knew that. She opened up her production log documents, scrolled to the top and handed the laptop to Ravi. ‘This is everything so far,’ she said.

He read through it quietly and then handed the computer back, a thoughtful look on his face.

‘OK, so the Sal alibi route is a dead end,’ he said. ‘After he left Max’s at ten thirty, I think he was alone because that explains why he panicked and asked his friends to lie for him. He could have just stopped on a bench on his walk home and played Angry Birds or something.’

‘I agree,’ said Pip. ‘He was most likely alone and therefore has no alibi; it’s the only thing that makes sense. So that line of enquiry is lost. I think the next step should be to find out as much as we can about Andie’s life and, in the process, identify anyone who might have had motive to kill her.’

‘Read my mind, Sarge,’ he said. ‘Maybe you should start with Andie’s best friends, Emma Hutton and Chloe Burch. They might actually speak to you.’

‘I’ve messaged them both. Haven’t heard back yet, though.’

‘OK, good,’ he said, nodding to himself and then to the laptop. ‘In that interview with the journalist, you talked about inconsistencies in the case. What other inconsistencies do you see?’