And then, three months ago, they’d come home late from a party to find the door to their flat forced open. Clara would never forget the creepy chill she’d felt as they silently walked around their home, knowing some stranger had recently been there – going through their things, touching their belongings. But the strange thing was, everything had been left in perfect order: nothing had been stolen; nothing, as far as she could tell, had been moved. Only a handwritten message on a page torn from Clara’s notepad was sitting on the kitchen table: I’ll be seeing you, Luke.

At least Luke had been sufficiently rattled to let Clara report that to the police. Who didn’t even turn up until the next day and discovered precisely nothing – the neighbours hadn’t seen anything, no fingerprints had been found – and as nothing had been taken or damaged, within days the so-called ‘investigation’ had quietly fizzled out.

Stranger still, after that, it was as if whoever it was had lost interest. For weeks now there’d been no new incidents, and Luke had been triumphant. ‘See?’ he’d said. ‘Told you they’d get bored eventually!’ But although Clara had tried hard to put it out of her mind, she hadn’t quite been able to forget the menace of that note – or the idea that the culprit was still out there somewhere, biding their time.

And now Luke had disappeared. What if ‘Barry’ had something to do with it? Even as she allowed the thought to form she could hear Luke’s laugh, see his eyes roll. ‘Jesus, Clara, will you stop being so dramatic?’ But as the morning progressed her sense of foreboding grew and when lunchtime came, instead of going to her usual café, she found herself walking back towards the Tube.

She reached Hoxton Square half an hour later, and when she caught sight of her squat, yellow-bricked building on its furthest corner, she was struck suddenly by the overwhelming certainty that Luke would be there waiting for her, and she ran the final few hundred yards, past the restaurants and bars, the black railings and shadowy lawn of the central garden and, out of breath by the time she reached the front door, she impatiently unlocked it before sprinting up the communal stairs to her flat. But when she got there, it was empty.