Fiona patted her shoulder. ‘Good girl. Now, we’re going to be practising your acting skills. Here’s what I need you to do.’

Fiona had been here two days ago – Monday, when Ethan’s record store was shut, so she didn’t have Rose – to double-check Max’s routine. She had figured out from calling his law firm – using a made-up name, putting on an English accent and pretending to be a prospective client – that he worked from home. Both days she’d watched him, he’d gone out to get lunch at the same time,eating it in the park, on the same bench. Looking very much like a man with a clear conscience; one who slept very well, thank you.

Did he ever think about her? Did Maisie’s face loom from the darkness of his subconscious? How about Fiona’s face? She didn’t know what guilt felt like, but was aware most people suffered from it. Did Max? Did he feel any responsibility at all?

‘Ready?’ she asked Rose. She knew he would be going out for lunch in five minutes. This was the perfect time.

The girl nodded.

‘Don’t be nervous. You’ll be fine.’

‘I’m not nervous.’

Fiona had undergone a trial once, wearing a heart rate monitor and taking a series of tests, both physical and mental. It had showed that, although her heart rate increased during exercise, like any normal person’s, it never increased or decreased due to stress, no matter how much she was put under. It increased a little when she was shown the right porn or particular images that were appealing to her. But she didn’t feel trepidation like regular people, and when she experienced fear it was practical, sensible – her body making her react to danger because it benefited her, kept her safe from harm.

She wished she had a heart rate monitor to measure Rose’s pulse now, to see if she was right about her.

Fiona went a little way along the road, standing behind a tree and peering around it. She watched Rose ring the doorbell then stand straight, shoulders back, the tin of cookies in her hand.

He came to the door and Fiona heard him speak, the drawl of his Essex accent, but couldn’t make out the words. She heard Rose’s voice next, and knew she would be telling him she was selling cookies to raise money to pay for an operation for her dog. She had a photo of Lola ready if he asked. Fiona knew that Max was a dog lover – it was possibly his only good feature – and that he would be a sucker for a pet-related sob story.

He pointed into the cookie tin, and Fiona knew what question he would be asking. This was another reason why she’d got Rose to bake the cookies with her. Rose shook her head and, satisfied, Max went back inside, presumably to look for some coins. She gave Rose a thumbs up. Rose didn’t respond, just stood there primly, arms wrapped around the cookie tin.

God, she was good.

Max reappeared and reached out a hand, passing Rose what looked like a five-pound note. He put his hand in the tin and took a couple of cookies.

Then Rose did what Fiona had instructed her to do. She asked Max if she could pop into his house and use his loo.

Fiona watched his face. He looked taken aback, then alarmed. She knew that, for all his faults, he wasn’t interested in little girls. But he would be very aware that the world was quick to be suspicious of men who had any interaction with kids who weren’t their own. What would the neighbours say if they saw a twelve-year-old girl going into or coming out of his house?

Fiona thought there was a very good chance he would say no and tell Rose to use the toilets in the park. But, after glancing around, he nodded, then pointed into the house. As Fiona had suspected, he was cautious. He stayed outside, holding the tin of cookies Rose had handed him, while she hurried inside.

Fiona crossed her fingers. Would Rose do her job properly now? While she waited, Fiona watched as Max peered into the cookie tin, glanced at the front door, then sneaked another one out and put it in his pocket.

The greedy sod.

Then he lifted his head. Rose must have called him from inside, just as Fiona had instructed her to do. He hesitated, then went through his front door.

Two minutes later, they both came out. Max shut the front door behind him, and Rose waved at him then walked towards Fiona, going straight past her as instructed. At the same time, Max strode off in the opposite direction, off to get his lunch.

When she was sure he wouldn’t look back, Fiona hurried after Rose and caught up with her on the corner.

‘How did it go?’ she asked immediately. ‘Did you get it?’

‘Three nine four four.’

His burglar alarm code, which his old-fashioned system required to be entered before leaving the house. Fiona had instructed Rose to watch closely as he punched the code in.

‘You’ve done brilliantly,’ Fiona said. ‘Now, all we need to do is get his keys, then I’ll be able to carry out this prank. Oh, it’s going to be—’

She stopped dead. Rose was holding out her hand, palm open. In it sat a pair of keys and, attached to them, a key fob with a label.

‘They were hanging on a nail on the wall outside the bathroom.’

Fiona took the keys and read the label.Front door spare.

‘He just leaves them hanging there?’ she said.