The agency had described the Hargrove household as a premium private residential placement with live-in accommodation, competitive salary, and scope for a long-term arrangement with a high-net-worth family.

What this meant, Maia Torres had learned in the three weeks since she'd started, was: a five-floor Kensington townhouse with twelve rooms she was expected to maintain to a standard that was not described in the contract but was very clear from Cassandra Hargrove's expression when she walked through the ground floor on Thursday mornings. Two children — Georgia and Finn, eight years old, twins, currently in the phase of childhood where they were pleasant to each other approximately forty percent of the time. A live-in room on the fourth floor that was, by the standards of anything she'd rented in London in the past four years, extraordinary: large, quiet, a window that looked over the garden, an ensuite bathroom with actual water pressure.

The salary was what made it all work. She was twenty-six and enrolled part-time in an interior design degree at Central Saint Martins, which she paid for by working, and the Hargrove salary plus the live-in arrangement meant that for the first time in two years she had enough breathing room to actually attend the lectures rather than scheduling work around them.

She had been prepared to be grateful and professional and invisible, which was the correct mode for a live-in household position with people who had more money than most countries.

She had been prepared for a lot of things. The Hargroves themselves, she had not been entirely prepared for.

Elliot Hargrove was forty-three and ran a hedge fund in the City with a portfolio that Maia had looked up because she was curious and had then looked away from because the numbers were not ones she had a framework for. He was the kind of man who filled a room differently from other men — not through height exactly, though he was tall, and not through noise, because he was often quiet. It was more the quality of his attention: when he was in a room, the room organised itself around him. This was not something he appeared to do deliberately. It was structural.

He was also, she had noticed with the specific attention of a woman who lived in the same building as a person and therefore had significant observational data, extremely controlled. This was the word she kept returning to. Controlled in the way he spoke, measured and precise. Controlled in the way he moved through the house — no wasted motion, everything purposeful. Controlled in the way he looked at his wife across the dinner table, which was a look that contained something large and leashed.

Cassandra Hargrove was thirty-nine and had been a commercial barrister for a decade before she'd left the bar to run a children's literacy charity, which she did with the efficiency of someone who had spent ten years in a profession where efficiency was survival. She was beautiful in the way of someone who was aware of her beauty as a professional instrument and used it accordingly. Dark hair, excellent posture, the specific quality of someone who was always thinking three steps ahead.

Maia had been living in their house for three weeks. In three weeks she had formed the following conclusions:

One, Elliot and Cassandra Hargrove were genuinely in love with each other in the specific way of people who had been together long enough that the love had transformed from feeling into architecture — it held the house up.

Two, they had a private life that was significantly more interesting than their public one.

She had formed this second conclusion on the basis of two pieces of evidence. The first was a conversation she'd overheard — not intentionally, she'd been on the second-floor landing collecting laundry and they'd been in the master bedroom with the door not fully closed — in which Cassandra had said something she couldn't quite hear and Elliot had replied: Not on a school night, Cass. But I'll think about Friday. And Cassandra had made a sound that was not the sound of a woman discussing dinner reservations.

The second was the door at the end of the third-floor corridor.