And it was enviably true. Steph didn’t need a fanfare of accessories to make a statement: Her height, cheekbones, and general aura did the job without fuss. But Steph would dismiss any attempt to compliment her in return, then whisk off to work or back up to her family before the conversation could progress. Emma would be left with the drift of her perfume in the empty hall, and a lingering curiosity about the woman she’d shared a front door with for nearly ten months. She didn’t know what Steph did for a living, but assumed she was successful; didn’t know how old she was, but guessed at early forties, and wondered whether forty was the point at which you stopped doing ridiculous things, like buying antisocial hamsters or generally making a mess of your life.

Steph had fallen quiet now. A drumming vibrated the dusty air, and Emma imagined her neighbor’s hundred-quid heel tapping the floor above. She reached up as if to feel the beat in the low ceiling, jerked away at Steph’s returning voice: “Paul, pick up! Have you heard from Frey?”

Now it was Paul Harlow’s image that filled her mind. Tall and athletic, maybe mid-fifties, his sandy hair a touch darker than his wife’s creamy highlights and his daughter’s white-blonde ponytail. Most mornings he rocketed past Emma when they were both out jogging by the Thames, his bulky headphones like a vise around his serious, determined face. He’d nod a brief greeting as he lapped her coming back the other way, and Emma would draw herself upright, trying not to look as exhausted as she felt.

Then there was Freya. The teenage daughter who apparently hadn’t come home at her usual time, who’d upset the family routine that played out upstairs each evening. When Emma glimpsed Freya it was usually in full flight: running on deer-like legs for the bus, or sometimes racing her dad along the river path, overtaking Emma with matching ease. The girl oozed energy with her swinging, sun-catching ponytail, her Fred Perry rucksack bouncing on her shoulders. Emma had come to recognize her gait up or down their stairs: She’d take them in leaps or descend at a gallop, one of her parents trailing behind with a fond shout, “Don’t worry, Freya, I can manage all the stuff . . .”

Emma had to admit she’d taken to peeking out of the window when she heard the Harlows leaving or arriving. Had started noticing the various combinations in which they went out or came home: Freya-Paul, Steph-Freya, Paul-Steph, all three together. With or without Waitrose bags, or takeaway cartons (Friday treat), or fresh bread that would infuse the building with its smell.

Clearly Emma didn’t have enough to occupy her. Her once-busy days yawned empty and the Harlows’ seemed endlessly, beguilingly full.