In retrospect, Robin knew that her anniversary weekend had been doomed before it had even begun, down in the House of Commons crypt where she had turned down Strike’s request to tail Jimmy.

Trying to throw off her sense of guilt, she had confided Strike’s request to Matthew when he picked her up after work. Already tense due to the demands of navigating the Friday night traffic in the Land Rover, which he disliked, Matthew went on the offensive, demanding to know why she felt bad after all the slave labor Strike had had out of her over the past two years and proceeding to badmouth Strike so viciously that Robin had felt compelled to defend him. They were still arguing about her job an hour later, when Matthew suddenly noticed that there was neither wedding nor engagement ring on Robin’s gesticulating left hand. She never wore these when playing the unmarried Venetia Hall, and had entirely forgotten that she would not be able to retrieve them from Albury Street before leaving for the hotel.

“It’s our bloody anniversary and you can’t even remember to put your rings back on?” Matthew had shouted.

They drew up outside the soft golden brick hotel an hour and a half later. A beaming man in uniform opened the door for Robin. Her “thank you” was almost inaudible due to the hard, angry lump in her throat.

They barely spoke over their Michelin-starred dinner. Robin, who might as well have been eating polystyrene and dust, looked around at the surrounding tables. She and Matthew were by far the youngest couple there, and she wondered whether any of these husbands and wives had been through this kind of trough in their marriages, and survived it.

They slept back to back that night.

Robin woke on Saturday in the awareness that every moment in the hotel, every step through the beautifully cultivated grounds, with the lavender walk, the Japanese garden, the orchard and organic vegetable beds, was costing them a small fortune. Perhaps Matthew was thinking the same, because he became conciliatory over breakfast. Nevertheless, their conversation felt perilous, straying regularly into dangerous territory from which they retreated precipitately. A tension headache began pounding behind Robin’s temple, but she did not want to ask hotel staff for painkillers, because any sign of dissatisfaction might lead to another argument. Robin wondered what it would be like to have a wedding day and honeymoon about which it was safe to reminisce. They eventually settled on talking about Matthew’s job as they strolled the grounds.

There was to be a charity cricket match between his firm and another the following Saturday. Matthew, who was as good at cricket as he had been at rugby, was greatly looking forward to the game. Robin listened to his boasts about his own prowess and jokes about Tom’s inadequate bowling, laughed at the appropriate moments and made sounds of agreement, and all the time a chilled and miserable part of her was wondering what was happening right now in Bow, whether Strike had gone on the march, whether he was getting anything useful on Jimmy and wondering how she, Robin, had ended up with the pompous, self-involved man beside her, who reminded her of a handsome boy she had once loved.

For the first time ever, Robin had sex with Matthew that night purely because she could not face the row that would ensue if she refused. It was their anniversary, so they had to have sex, like a notary’s stamp on the weekend, and about as pleasurable. Tears stung her eyes as Matthew climaxed, and that cold, unhappy self buried deep in her compliant body wondered why he could not feel her unhappiness even though she was trying so hard to dissemble, and how he could possibly imagine that the marriage was a success.

She put her arm over her wet eyes in the darkness after he had rolled off her and said all the things you were supposed to say. For the first time, when she said “I love you, too,” she knew, beyond doubt, that she was lying.

Very carefully, once Matthew was asleep, Robin reached out in the darkness for the phone that lay on her bedside table, and checked her texts. There was nothing from Strike. She Googled pictures of the march in Bow and thought she recognized, in the middle of the crowd, a tall man with familiar curly hair, who was wearing a Guy Fawkes mask. Robin turned her mobile face down on the bedside table to shut out its light, and closed her eyes.