“I told you,” she said. “I gave you a lift home from yoga. And today I was out and drove past your house and saw the For Sale sign. I’m having a baby.” She gave me a sidelong glance and I flushed scarlet. “As you know. I’m looking for a new house. And I saw your car outside so I thought I’d pop in and ask for a look around.”

I stared at her. “You want to live here?”

“No, of course I don’t!” She sighed as though I was stupid. “That’s what I’ll tell them.”

I could hear the sound of a siren; it sounded as though it was a way away, but it was hard to tell. Panic was rising in me and I felt like I wanted to run on the spot.

She said, “Tell me how we know each other.”

I was terrified; would I have to tell her I’d driven past her house and seen her kissing Harry? “I didn’t mean to . . .”

“Forget that,” she said urgently. “Tell me what I said.”

“We went to yoga.”

“That’s right. Good. It was a beginners’ class. We were useless and stopped going. It was ten pounds an hour. In Matthew Street. Two or three years ago. We didn’t know each other beforehand. We haven’t seen each other since.”

Finally I got it. I nodded.

“And tell me where you were when Tom fell downstairs.”

“I was here,” I said, slowly. I’d stopped crying by now. I knew how vital this was. “He was showing people around the house; they seemed to like it. After they left he popped up to his office to look for his iPad. We wanted to check what other houses in the street had sold for. I was waiting for him to come downstairs. And I also wanted to talk to him about Josh’s eighteenth birthday. I wanted to ask Tom what I could buy him.”

I stopped dead in my tracks, realizing that Josh had just lost his father. All the breath seemed to leave my body and I could feel my eyes bulging. Emma jumped up and put my head in my lap, telling me to breathe, that everything would be all right. I knew it wouldn’t, though. Not for Josh.

“What happened then?” she whispered in my ear. “What are you going to say happened then?”

It took a huge effort to lift my head up. She was giving me an encouraging look, her face pale but resolute.

“I heard a crash and a shout,” I said, remembering my lines. “I rushed out into the hallway.”

“I know,” she said. “I saw you.”

“He was at the bottom of the stairs.” At last this part was true. I started to cry. “His body was twisted and his eyes were shut and his ear was bleeding.”

“And then?”