I knew before I rang the bell and knocked with the heavy brass ring that no one was there: there were no lights on in any of the windows, no car parked in the driveway; the house had an unoccupied look. But I stood, stamping my feet in the cold, waiting to make sure. I opened the letterbox and saw only the polished floor. I peered through the downstairs window and saw the tidy, empty living room, the swept hearth, the gleaming top of a grand piano with photographs on top in silver frames. It was too arranged and perfect, like a stage set rather than a home. I wondered what Hugo Livingstone was feeling now. Was he lonely, angry, sad? Did he think about Greg as I thought about Milena, with hatred, jealousy and puzzlement? Did he think about me? Did he know something I didn’t?

That morning, when I had sat over my unsatisfactory breakfast of slightly stale bread and the last scrapings of marmalade, I had decided I needed to look at the picture from the other side. I had examined Greg’s life and found nothing, but what about Milena’s? Although to say that I had ‘decided’ is inaccurate, because what had actually happened was that I had drifted round the house, at a loss as to what to do with myself, picking things up and putting them down, opening the fridge and closing it, shuffling out through the garden, which was neglected and piled with soggy leaves, unlocking the shed door and gazing at the furniture waiting for my attention. Then I’d put on my coat, wrapped a scarf round my neck and walked to the Underground station, without even saying to myself that I was going back to the Livingstones’ house and certainly without knowing what I hoped to find there. Silvio, smiling sarcastically, a signed and dated love letter from Greg to Milena, with a photo of the besotted couple together? His father, assuring me that his wife had never had an affair with Greg and he could prove it with – with what? Nothing could prove that.

There I was, on a damp, grey November morning, staring at the blank windows of the large house and wondering miserably what to do next. Because I couldn’t return to my own small, cold house and deal with the things that were piling up: bills, letters, phone messages, laundry, dead leaves, broken chairs, dust, dirt and drabness. I found myself consulting my map and walking the half-mile or so from the Livingstone house to the address of Party Animals, the business Milena and her partner had run together.

I’d looked at the company website, read about parties at the Tower of London and the zoo, fancy-dress balls, colour-coordinated golden weddings, Burns Night celebrations, with haggis created especially for people who didn’t like haggis, and dinners for your most valued clients with six elegant courses. I thought about the parties Greg and I had had – you invite people round at the last moment to squash into the front room, ask them to bring wine, then cook chilli con carne and garlic bread, put on some music and see what happens.

Tulser Road was a quiet residential street just down from Vauxhall Bridge. It didn’t look like the kind of place for offices and, indeed, number eleven was clearly just a house, like the other houses on either side: large and semi-detached, with a side alley leading to its garden, a basement floor and bay windows. There was only one bell, and no sign saying that this was where exciting and original happenings, tailor-made to suit every individual customer, were organized. But there were lights on in the downstairs window; someone was there, at least. I raised my hand to ring the bell and saw my wedding ring. I looked at it for a moment, almost dispassionately, as if it had suddenly appeared. In fact I hadn’t taken it off since – with a great deal of effort – Greg had pushed it over my knuckle in the register office. I had thought it would be difficult to get off but I’d lost weight and it made no resistance. It was an object now, not part of me. I put it into my purse and rang the bell.

The woman who answered the door was slightly older than I had expected; she was tall and slender, with long legs and unexpectedly full breasts. Her highlighted blonde hair was cut short in a chic style with soft wisps framing her triangular face. Her pale skin was just beginning to line, and she wore thick, rectangular specs. She had on beautifully tailored black trousers and a pale blue linen shirt, tiny studs in her ears and a thin silver chain round her neck. If she was wearing makeup, it was the invisible kind. There was a classy look to her, a restrained and intelligent attractiveness that I liked immediately.

‘Yes?’ she said. ‘Can I help you?’ Her voice was low and husky; her manner was polite, but a little impatient. From somewhere in the house there was a loud bang, the sound of something dropped. I saw her wince and bite her lip.

‘Is this where Party Animals is run from?’

‘That’s right. Are you planning an event?’

‘No,’ I said. ‘I’ve come about Milena Livingstone.’

I saw her eyes widen and then she made a visible effort to control herself. She reminded me of me. I recognized the weary sense that the story would have to be told yet again.

‘Are you a friend of hers?’ Without giving me time to answer, she said, ‘Didn’t you know?’

There was a fraction of a moment when I could have said, yes, I knew, because the man she died with was my husband. But something stopped me. ‘Know what?’ I said.

‘Come in for a second. Sorry, my name’s Frances Shaw.’

She held out a hand and I shook it. Her grip was warm, strong; I saw that her nails were painted the palest pink. I stepped over the threshold and she shut the door behind us, then led me along a corridor.

‘Better come downstairs into the office, if you can call it that. I’m in total chaos, I’m afraid.’ She led me into the basement, a large room with a long table in the centre; on its surface were several roughly stacked heaps of paper and files. There was a sofa covered with brochures and a desk pushed up against the wall, also piled high with folders.

A phone was ringing and a young woman, with dramatically dark eye-shadow and very high-heeled boots, came out of the adjoining room. ‘Shall I get that?’ she asked.

‘No, let the machine answer it,’ said Frances. ‘I tell you what, though, Beth, perhaps you could make us a cup of coffee. If you want coffee, that is,’ she added, turning to me.

‘Coffee would be lovely.’ I was a bit dazed.

‘Have a seat.’ Frances scooped up the brochures from the sofa, looked at them helplessly, then laid them on the floor. ‘When did you last see Milena?’

‘I don’t want to give you the wrong impression…’ I said.

The phone rang again and then her mobile, which was lying on the table. ‘Damn. Sorry. I’ll be with you in a second.’ She flipped it open and turned away from me. I heard her murmuring something. Upstairs, cupboard doors banged and Beth’s heels clicked across the floor. I sat on the sofa, taking off my jacket. The warm, cluttered room was like a nest.

Frances snapped shut her mobile and sat beside me. ‘I’m surprised you haven’t heard. I’m so sorry to have to tell you that Milena died.’

That was my last chance to say who I was, but I didn’t. I wasn’t even sure why. Perhaps it was a relief to be the onlooker for a while, rather than the victim.

‘Oh!’ I said, and rubbed my face because I wasn’t sure what my expression should be.

‘This must be a shock.’

‘I wasn’t exactly close to her,’ I said, which was true.

‘She died recently in a car crash.’

‘How terrible,’ I muttered. I felt like an actor, saying lines that made little sense to me.

‘It was awful. She was with a man.’ There was a pause. ‘Someone nobody knew even existed.’

‘So young,’ I said. The possibility of putting Frances straight receded, and then – as she told me Milena’s husband and her step-children were coping as well as could be expected and I expressed sympathy – it vanished altogether.