When I appeared the next morning Agnes was seated beside her husband at the breakfast table, her head resting on his shoulder as he murmured into her ear, their fingers entwined. She apologized formally to Ilaria as he watched, smiling, and when he left for work she swore furiously, in Polish, for the whole time it took us to jog around Central Park.

That evening she announced she was going to Poland for a long weekend, to see her family, and I felt a faint relief when I gathered she did not want me to come too. Sometimes being in that apartment, enormous as it was, with Agnes’s ever-changing moods and the swinging tensions between her and Mr Gopnik, Ilaria and his family felt impossibly claustrophobic. The thought of being alone for a few days felt like a little oasis.

‘What would you like me to do while you’re gone?’ I said.

‘Have some days off!’ she said, smiling. ‘You are my friend, Louisa! I think you must have a nice time while I am away. Oh, I am so excited to see my family. So excited.’ She clapped her hands. ‘Just to Poland! No stupid charity things to go to! I am so happy.’

I remembered how reluctant she had been to leave her husband even for a night when I had arrived. And pushed the thought away.

When I walked back into the kitchen, still pondering this change, Ilaria was crossing herself.

‘Are you okay, Ilaria?’

‘I’m praying,’ she said, not looking up from her pan.

‘Is everything all right?’

‘Is fine. I’m praying that that puta doesn’t come back again.’

I emailed Sam, the germ of an idea flooding me with excitement. I would have rung him, but he had been silent since our phone call and I was afraid he was still annoyed with me. I told him I had been given an unexpected three-day weekend, had looked up flights and thought I might splurge on an unexpected trip home. So how about it? What else were wages for? I signed it with a smiley face, an aeroplane emoji, some hearts and kisses.

The answer came back within an hour.

Sorry. I’m working flat out and Saturday night I promised to take Jake to the O2 to see some band. It’s a nice idea but this isn’t a great weekend. S x

I stared at the email and tried not to feel chilled. It’s a nice idea. It was as if I’d suggested a casual stroll around the park.

‘Is he cooling on me?’

Nathan read it twice. ‘No. He’s telling you he’s busy and this isn’t a great time for you to come home unexpectedly.’

‘He’s cooling on me. There’s nothing in that email. No love, no … desire.’

‘Or he might have been on his way to work when he wrote it. Or on the john. Or talking to his boss. He’s just being a bloke.’

I didn’t buy it. I knew Sam. I stared at those two lines again and again, trying to dissect their tone, their hidden intent. I went on Facebook, hating myself for doing so, and checked to see whether Katie Ingram had announced that she was doing something special that weekend. (Annoyingly, she hadn’t posted anything at all. Which was exactly what you would do if you were planning to seduce someone else’s hot paramedic boyfriend.) And then I took a breath and wrote him a response. Well, several responses, but this was the only one I didn’t delete.

No problem. It was a long shot! Hope you have a lovely time with Jake. Lx

And then I pressed ‘send’, marvelling at how far the words of an email could deviate from what you actually felt.

Agnes left on the Thursday evening, laden with gifts. I waved her off with big smiles and collapsed in front of the television.

On Friday morning I went to an exhibition of Chinese opera costumes at the Met Costume Institute and spent an hour admiring the intricately embroidered, brightly coloured robes, the mirrored sheen of the silks. From there, inspired, I travelled to West 37th to visit some fabric and haberdashery stores I had looked up the previous week. The October day was cool and crisp, heralding the onset of winter. I took the subway, and enjoyed its grubby, fuggy warmth. I spent an hour scanning the shelves, losing myself among the bolts of patterned fabric. I had decided to put together my own mood board for Agnes for when she returned, covering the little chaise longue and the cushions with bright, cheerful colours – jade greens and pinks, gorgeous prints with parrots and pineapples, far from the muted damasks and drapes that the expensive interior decorators kept offering her. Those were all First Mrs Gopnik colours. Agnes needed to put her own stamp on the apartment – something bold and lively and beautiful. I explained what I was doing, and the woman at the desk told me about another shop, in the East Village – a second-hand clothes outfit where they kept bolts of vintage fabric at the back.

It was an unpromising storefront – a grubby 1970s exterior that promised a ‘Vintage Clothes Emporium, all decades, all styles, low prices’. But I walked in and stopped in my tracks. The shop was a warehouse, set with carousels of clothes in distinct sections under homemade signs that said ‘1940s’, ‘1960s’, ‘Clothes That Dreams Are Made Of’, and ‘Bargain Corner: No Shame In A Ripped Seam’. The air smelt musky, of decades-old perfume, moth-eaten fur and long-forgotten evenings out. I gulped in the scent like oxygen, feeling as if I had somehow recovered a part of myself I had barely known I was missing. I trailed around the store, trying on armfuls of clothes by designers I had never heard of, their names a whispered echo of some long-forgotten age – Tailored by Michel, Fonseca of New Jersey, Miss Aramis – running my fingers over invisible stitching, placing Chinese silks and chiffon against my cheek. I could have bought a dozen things, but I finally settled on a teal blue fitted cocktail dress with huge fur cuffs and a scoop neck (I told myself fur didn’t count if it dated from sixty years ago), a pair of vintage denim railroad dungarees and a checked shirt that made me want to chop down a tree or maybe ride a horse with a swishy tail. I could have stayed there all day.

‘I’ve had my eye on that dress for soooo long,’ said the girl at the checkout desk, as I placed it on the counter. She was heavily tattooed, her dyed black hair swept up in a huge chignon and her eyes lined with dark kohl. ‘But I couldn’t get my tush into it. You looked cute.’ Her voice was raspy, thickened by cigarettes and impossibly cool.

‘I have no idea when I’ll wear it, but I have to have it.’

‘That’s how I feel about clothes all the time. They talk to you, right? That dress has been screaming at me: Buy me you idiot! And maybe lay off the potato chips!’ She stroked it. ‘Bye-bye, little blue friend. I’m sorry I let you down.’

‘Your store is amazing.’

‘Oh, we’re hanging in here. Buffeted by the cruel winds of rent rises and Manhattanites who would rather go to TJ Maxx than buy something original and beautiful. Look at that quality.’ She held up the lining of the dress, pointing to the tiny stitches. ‘How are you going to get work like that out of some sweat shop in Indonesia? Nobody in the whole of New York state has a dress like this.’ She raised her eyebrows. ‘Except you, British lady. Where is that beauty from?’

I was wearing a green military greatcoat that my dad joked smelt like it had been in the Crimean War, and a red beanie. Underneath I had my turquoise Dr Martens boots, a pair of tweed shorts and tights.

‘I’m loving that look. You ever wanna offload that coat, I could sell it like that.’ She snapped her fingers so loudly that my head shot backwards. ‘Military coats. Never get tired. I have a red infantry coat that my grandma swears she stole from a guardsman at Buckingham Palace. I cut the back off and turned it into a bum-freezer. You know what a bum-freezer is, right? You wanna see a picture?’