Liv flicks through two sheets. Here the text is more dense, and interrupted by a formal sepia-tinted photograph of Édouard Lefèvre, gazing into the middle distance.

October 1914

The Gare du Nord was heaving, a boiling sea of soldiers and weeping women, the air thick with smoke and steam and the anguished sounds of goodbye. I knew Édouard wouldn’t want me to cry. Besides, this would only be a short separation; all the newspapers said as much.

‘I want to know everything you’re doing,’ I said. ‘Make lots of sketches for me. And be sure to eat properly. And don’t do anything stupid, like getting drunk and fighting and getting yourself arrested. I want you home as quickly as possible.’

He made me promise that Hélène and I would be careful. ‘If you get wind that the enemy line is moving anywhere towards you, promise me you will come straight back to Paris.’

When I nodded, he said, ‘Don’t give me that sphinx face, Sophie. Promise me you will think of yourself first. I will not be able to fight if I believe you might be in danger.’

‘You know I’m made of strong stuff.’

He glanced behind him at the clock. Somewhere in the distance a train let out a piercing whistle. Steam, the stench of burned oil, rose around us, briefly obscuring the crowds on the platform. I reached up to adjust his blue serge kepi. Then I stood back to look at him. What a man my husband is! A giant among men. His shoulders so broad in his uniform, half a head taller than anyone else there. He is such a huge physical presence; to look at him made my heart swell. I don’t think I believed even then that he was actually leaving.

He had finished a little gouache painting of me the week before. He patted his top pocket now. ‘I will carry you with me.’

I touched my heart with my hand. ‘And you with me.’ I was secretly envious that I hadn’t one of him.

I glanced around me. Carriage doors were opening and closing, hands reaching past us, fingers entwining for the last time.

‘I’m not going to watch you go, Édouard,’ I told him. ‘I shall close my eyes and keep the image of you as you stand before me.’

He nodded. He understood. ‘Before you go,’ he said suddenly. And then he swept me to him and kissed me, his mouth pressed against mine, his big arms pulling me tight, tight to him. I held him, my eyes squeezed shut, and I breathed him in, absorbing the scent of him, as if I could make that trace of him last for his entire absence. It was as if only then I believed he was actually going. My husband was going. And then, when it became too much, I pushed myself away, my face rigidly composed.

I kept my eyes closed, and gripped his hand, not wanting to see whatever was on his face, and then I turned swiftly, straight-backed, and pushed my way through the crowds, away from him.

I don’t know why I didn’t want to see him actually get on the train. I have regretted it every day since.

It was only when I got home that I reached into my pocket. I found a piece of paper he must have slipped in there while he held me: a little caricature of the two of us, him a huge bear in his uniform, grinning, his arm around me, petite and narrow-waisted, my face straight and solemn, my hair pulled neatly behind my head. Underneath it he had written, in his looping, cursive script: ‘I never knew real happiness until you.’

Liv blinks. She places the papers neatly in the folder. She sits, thinking. Then she unrolls the picture of Sophie Lefèvre, that smiling, complicit face. How could Monsieur Bessette be right? How could a woman who adored her husband like that betray him, not just with another man but with an enemy? It seems incomprehensible. Liv rolls up the photocopy and places her notes back inside her bag.

Mo pulls off her earphones. ‘So. Half an hour to St Pancras. Do you think you got what you wanted?’

She shrugs. She cannot speak past the huge lump that has risen in her throat.

Mo’s hair is scraped back into jet-black furrows from her face, her cheeks milk pale. ‘You nervous about tomorrow?’

Liv swallows and flashes a weak smile. She has thought about almost nothing else for the past six weeks.

‘For what it’s worth,’ Mo says, as if she has been thinking about it for some time, ‘I don’t think McCafferty set you up.’

‘What?’

‘I know loads of crappy, mendacious people. He’s not one of them.’ She picks at a piece of skin on her thumb, then says, ‘I think Fate just decided to play a really sick joke and dump you both on opposing sides.’

‘But he didn’t have to come after my painting.’

Mo lifts an eyebrow. ‘Really?’

Liv stares out of the window as the train rolls towards London, fighting a new lump in her throat.

Across the table, the couple bedecked in tinsel are leaning against each other. They have fallen asleep, their hands entwined.

Later she is not entirely sure what makes her do it. Mo announces at St Pancras that she is heading over to Ranic’s house, leaving Liv with instructions not to stay on the Internet all night looking up obscure restitution cases, and to please stick that Camembert in the fridge before it escapes and poisons the whole house. Liv stands in the teeming concourse, holding a plastic bag of stinking cheese and watching the little dark figure as she heads towards the Underground, a bag slung nonchalantly over her shoulder. There is something both jaunty and solid in the way Mo talks about Ranic; a sense that something has shifted for both of them.

She waits until Mo has vanished into the crowd. The commuters wash around and past her, a stepping-stone in a stream of people. They are all in pairs, arms linked, chatting, casting fond, excited looks at each other, or if alone, head down, determinedly heading home to the person they love. She sees wedding bands, engagement rings, hears snatches of murmured conversations about train times, last-minute pints of milk, and Can you pick me up from the station? Afterwards she will think sensibly about the many people who dread the partner they return to, look for excuses not to board the train, hide in bars. But for now the bored people, the miserable people, the other lonely people are invisible. She reads the crowd as if it can only be an affront to her single state. I was one of you once, she thinks, and can’t quite imagine what it would be like to be one of them again.