Their landlord, a publisher who was off to New York to work at head office, had been delighted with his new tenants. A gay man in his forties, he admired Matthew’s clean-cut looks and made a point of handing over the keys personally on their moving day.

“I agree with Jane Austen on the ideal tenant,” he told Matthew, standing in the cobbled street. “‘A married man, and without children; the very state to be wished for.’ A house is never well cared for without a lady! Or do you two share the hoovering?”

“Of course,” Matthew had said, smiling. Robin, who was carrying a box of plants over the threshold behind the two men, had bitten back a caustic retort.

She had a suspicion that Matthew was not disclosing to friends and workmates that they were tenants rather than owners. She deplored her own increasing tendency to watch Matthew for shabby or duplicitous behavior, even in small matters, and imposed private penances on herself for thinking the worst of him all the time. It was in this spirit of self-castigation that she had agreed to the party, bought alcohol and plastic tumblers, made food and set everything up in the kitchen. Matthew had rearranged the furniture and, over several evenings, organized a playlist now blaring out of his iPod in its dock. The first few bars of “Cutt Off” by Kasabian started as Robin hurried upstairs to change.

Robin’s hair was in foam rollers, because she had decided to wear it as she had on their wedding day. Running out of time before guests were due, she pulled out the rollers one-handed as she yanked open the wardrobe door. She had a new dress, a form-fitting pale gray affair, but she was afraid that it drained her of color. She hesitated, then took out the emerald-green Roberto Cavalli that she had never worn in public. It was the most expensive item of clothing she owned, and the most beautiful: the “leaving” present that Strike had bought her after she had gone to him as a temp and helped him catch their first killer. The expression on Matthew’s face when she had excitedly shown him the gift had prevented her ever wearing it.

For some reason her mind drifted to Strike’s girlfriend, Lorelei, as she held the dress up against herself. Lorelei, who always wore jewel-bright colors, affected the style of a 1940s pin-up. As tall as Robin, she had glossy brunette hair that she wore over one eye like Veronica Lake. Robin knew that Lorelei was thirty-three, and that she co-owned and ran a vintage and theatrical clothing store on Chalk Farm Road. Strike had let slip this information one day and Robin, making a mental note of the name, had gone home and looked it up online. The shop appeared to be glamorous and successful.

“It’s a quarter to,” said Matthew, hurrying into the bedroom, stripping off his T-shirt as he came. “I might shower quickly.”

He caught sight of her, holding the green dress against herself.

“I thought you were wearing the gray one?”

Their eyes met in the mirror. Bare-chested, tanned and handsome, Matthew’s features were so symmetrical that his reflection was almost identical to his real appearance.

“I think it makes me look pale,” said Robin.

“I prefer the gray one,” he said. “I like you pale.”

She forced a smile.

“All right,” she said. “I’ll wear the gray.”

Once changed, she ran fingers through her curls to loosen them, pulled on a pair of strappy silver sandals and hurried back downstairs. She had barely reached the hall when the doorbell rang.

If she had been asked to guess who would arrive first, she would have said Sarah Shadlock and Tom Turvey, who had recently got engaged. It would be like Sarah to try and catch Robin on the hop, to make sure she had an opportunity to nose around the house before anybody else, and to stake out a spot where she could look over all the arrivals. Sure enough, when Robin opened up, there stood Sarah in shocking pink, a big bunch of flowers in her arms, Tom carrying beer and wine.

“Oh, it’s gorgeous, Robin,” crooned Sarah, the moment she got over the doorstep, staring around the hall. She hugged Robin absentmindedly, her eyes on the stairs as Matthew descended, doing up his shirt. “Lovely. These are for you.”

Robin found herself encumbered by an armful of stargazer lilies.

“Thanks,” she said. “I’ll just go and put them in water.”

They didn’t have a vase big enough for the flowers, but Robin could hardly leave them in the sink. She could hear Sarah’s laugh from the kitchen, even over Coldplay and Rihanna, who were now belting out “Princess of China” from Matthew’s iPod. Robin dragged a bucket out of the cupboard and began to fill it, splattering herself with water in the process.

The idea had once been mooted, she remembered, that Matthew would refrain from taking Sarah out for lunches during their office lunch hours. There had even been talk of stopping socializing with her, after Robin had found out that Matthew had been cheating with Sarah in their early twenties. However, Tom had helped Matthew get the higher-paid position he now enjoyed at Tom’s firm, and now that Sarah was the proud owner of a large solitaire diamond, Matthew did not seem to think that there should be the slightest awkwardness attached to social events including the future Mr. and Mrs. Turvey.

Robin could hear the three of them moving around upstairs. Matthew was giving a tour of the bedrooms. She heaved the lily-filled bucket out of the sink and shoved it into a corner beside the kettle, wondering whether it was mean-spirited to suspect that Sarah had brought flowers just to get Robin out of the way for a bit. Sarah had never lost the flirtatious manner towards Matthew she had had since their shared years at university.

Robin poured herself a glass of wine and emerged from the kitchen as Matthew led Tom and Sarah into the sitting room.

“… and Lord Nelson and Lady Hamilton are supposed to have stayed in number 19, but it was called Union Street then,” he said. “Right, who wants a drink? It’s all set up in the kitchen.”

“Gorgeous place, Robin,” said Sarah. “Houses like this don’t come up that often. You must’ve got really lucky.”

“We’re only renting,” said Robin.

“Really?” said Sarah beadily, and Robin knew that Sarah was drawing her own conclusions, not about the housing market, but about Robin and Matthew’s marriage.

“Nice earrings,” said Robin, keen to change the subject.

“Aren’t they?” said Sarah, pulling back her hair to give Robin a better view. “Tom’s birthday present.”

The doorbell rang again. Robin went to answer it, hoping that it would be one of the few people she had invited. She had no hope of Strike, of course. He was bound to be late, as he had been to every other personal event to which she had invited him.

“Oh, thank God,” said Robin, surprised at her own relief when she saw Vanessa Ekwensi.

Vanessa was a police officer: tall, black, with almond-shaped eyes, a model’s figure and a self-possession Robin envied. She had come to the party alone. Her boyfriend, who worked in Forensic Services at the Met, had a prior commitment. Robin was disappointed: she had looked forward to meeting him.

“You all right?” Vanessa asked as she entered. She was carrying a bottle of red wine and wearing a deep purple slip dress. Robin thought again of the emerald-green Cavalli upstairs and wished she had worn it.

“I’m fine,” she said. “Come through to the back, you can smoke there.”