She rubbed her eyes wearily. ‘It was such a mess, though. Not just because I was married – for a bit that hardly bothered me. He’d had a thing with Milena first.’

I managed to make a small sound. My heart felt large and painful.

‘Just a fling, really, but you know what Milena was like. She didn’t take it well that he preferred me. That was putting it mildly. She hated me, really hated me. I felt her hatred would literally scorch me when I walked into the room.’ Frances shuddered. ‘And then she died.’

‘So this man,’ I said, ‘she knew you were with him?’

‘Oh, yes. Milena always knew everything.’

‘Was he married as well?’ I barely recognized my own voice.

‘What do you think, Gwen? Yes, he was married.’

‘Who was he?’

Her expression hardened. ‘That’s not what it’s about,’ she said, in a tone almost of distaste. ‘What does that matter?’

‘I didn’t mean…’

‘It’s over, that’s all that matters.’ She gave a laugh that wasn’t really a laugh at all, closer to a sob. ‘Something happened. I still can’t make sense of it, Gwen. It’s tormenting me. That was why I had to tell someone – otherwise I’ll go mad.’

She leaned forward, and at that moment there was a ring at the front door. She straightened. ‘That’ll be my cab.’ She gave me a rueful smile. ‘To be continued,’ she said, and with that she was gone, tossing her gorgeous coat over her shoulders, picking up her bag, throwing me a pleading smile, running up the stairs. I heard the front door slam.

After she had gone I stayed where I was. I was trying to breathe. I felt as though I had knives in my chest and each small inhalation hurt. It was several minutes before I felt able to get up, but even then I stood in the middle of the room, not sure what to do next. Thoughts hissed in my brain. Everything was murky and confused.

But I had come here to work and work I did: I went through the brochure very carefully and marked it up for the printers. When Beth arrived, I gave it to her to check. I had worried that she might be resentful, but Beth never resented anything that made her workload even lighter than it was already. While she leafed through it and talked on the phone and made tea, I filed the few remaining invoices and receipts; I answered calls when they came in; I even tidied the room a bit. And all the time the phone was in my pocket with its single missed call. The more I tried to put it out of my mind, the more it occupied it, so that by the middle of the day it was all I could think about. That, and Frances’s secret, the one that had been rotting away inside her and was now out in the open.

I couldn’t call the number because what would I say? Yet if I didn’t call, what had been the point of going to all that effort? Maybe I should try and match the number with one in Milena’s various address books. I started and quickly gave it up as impossible.

I went out to the deli down the road and bought lunch for the two of us: paninis stuffed with roasted vegetables, green pesto and melted mozzarella. While we ate, Beth asked me about my life and quickly shifted the conversation back to hers. We were both more comfortable with that and she told me about the failings of her current boyfriend.

Afterwards I shuffled pieces of paper. I put books back on shelves. I took the phone out of my pocket and laid it on the desk. I put it away again: out of sight, out of mind, I instructed myself sternly. I made more coffee, very strong this time, which I drank while it was still too hot so it burned my tongue and the roof of my mouth. I took the phone out once more, stared at it as if it could talk. I fed unwanted mail through the shredder and watered the plants on the window-sill. When Beth left for the day, I couldn’t stop myself. I took my phone, pulled up the missed-call window and pressed call, then cancelled it immediately.

I pressed the number again and this time I held my nerve. I could hear it ringing now and closed my eyes, swallowing hard, trying to breathe normally in spite of the rushing in my head and the pounding in my ears.

‘Hello?’ said a male voice down the phone. And ‘Hello?’ it said, outside the door.

‘Who…?’ I began in confusion, before realization flooded through me. I jabbed end call and slammed the phone on the desk. It skittered along the shiny surface and clattered to the floor.

‘Hello?’ said the voice outside the door again, irritable now. ‘Are you there? Hello? Hello?’

I was trembling so much I could barely sit upright. The door swung open.

‘Hi, Gwen,’ said David, pushing his mobile back into his pocket.

I pretended I was so hard at work that I hadn’t heard him properly. I stared at some figures and underlined a few. My hands shook and the pen made incomprehensible scrawls across the page. David, I thought. So it was David.

‘Gwen?’

I felt unable to speak coherently. I could barely manage to breathe. But I made myself say something, as if I were a normal human being. ‘David,’ I said, ‘how are you doing?’

Although he had spoken to me, he didn’t seem to hear my reply. He just wandered restlessly around the office. I stared at the paper, and tried to make sense of what I had just learned. There was so much of it that I could only process it in fragments. David was one of Milena’s lovers. Those tender, effusive emails had been from him – he was usually so ironic and amused. Milena had sat in this office reading his messages, writing to him, while Frances had been in the same room just a few feet away. How could he have done it? With her friend and colleague? Right under her nose? How could she have done it? Or was I reading it the wrong way? Was that part of the excitement? They say that there’s no point in gambling for small amounts of money. It has to hurt when you lose. Maybe it’s the same with infidelity. Anyone can have a one-night stand on a business trip, at a conference in another country. The real thrill is doing it like an illusionist, risking discovery at every moment, witnessing your victim’s lack of knowledge.

When I thought of Milena’s messages, the chill of them, the manipulation, I wondered if she was more interested in the power than in the sex. Was sex for her just a demonstration that she could have any man she wanted? That she could triumph over any woman, in any circumstances? Was it likely that Greg could have held out against that? Was he so different from the others?

I tried to remember what David had said to me about Milena and Frances. In all those conversations when I had been lying to him, he had been lying to me, as he had also been lying – had he? – to Johnny and Frances. Well, if he had, he wasn’t the only liar. There was Frances, with her own infidelity. They had been betraying each other.

‘Is Frances around?’

I felt like someone very, very drunk trying to imitate someone sober and not knowing whether the act was convincing or ludicrous. ‘I don’t know,’ I said, enunciating each word carefully. ‘She’s seeing the printers some time this afternoon.’

‘Don’t worry,’ said David. ‘I can phone her.’

I couldn’t stand this any longer. I stood up and reached for my jacket. David gave me the appraising look I always found so hard to read.

‘I’m not driving you away, am I?’

‘I’ve got a meeting,’ I said. ‘I have to go.’

‘At your school?’ he asked.

‘No,’ I said, and stopped myself elaborating. I didn’t want to risk any lies I might trap myself inside. ‘Could you tell Frances I’ll give her a ring?’

I walked to the door. Just as I was opening it, I heard David call my name. What was it? Had I made a mistake?

‘Sorry, Gwen, I forgot.’

‘What?’

‘Do you want to come out to lunch with us tomorrow?’

‘Sure.’

‘Hugo Livingstone’s coming. We thought it would be good if you could join us. What with Milena, Hugo’s in a bad way. It would do him good to meet a friend.’