I took the bowl from Tristram and handed it to her, noticing that her pudgy hands were covered in rings. She dropped several lumps into a coffee cup then handed the bowl back to me, looking up expectantly as the cream slice arrived. I had scarcely turned back to my own coffee when I heard choking noises. I looked around. The fat lady was turning almost purple, her hands waving in the air in panic.

“She’s choking.” Tristram leaped up and began slapping her on the back. The waitress heard the commotion and rushed out to help. But it was no good. The woman’s choking turned to a gurgle and she collapsed onto her plate.

“Get help, quickly!” Tristram shouted. I stood there in a state of shock as the waitress ran out screaming.

“Can’t we do something?” I demanded. “Try and remove what’s choking her.”

“Whatever she swallowed is too far down or it would have come up by now. I’m scared I’d only wedge it more firmly if I tried anything.” Tristram looked ashen white. “How awfully horrible. Shall I take you home?”

“We should stay until help gets here,” I said, “even though I don’t see what we could do.”

“I’m afraid she asked for it,” he said. “Did you see the way she was cramming that cake into her mouth?”

Help arrived in the shape of a policeman and a doctor who had happened to be passing. The doctor set to work instantly, then took her pulse.

“I’m afraid there’s nothing we can do,” he said. “She’s dead.”

We gave our statements to the policeman and tiptoed home. Tristram had to go back to work and I tried to pack for the house party. Fig was off somewhere, probably annoying Scotland Yard again. I wandered around the empty house, trying to shake off a feeling of dread that just wouldn’t go away. If this had been my first brush with death, it would have been different. But within one week to have found a body in my bath, been dragged off a boat, then almost pushed under a train made this death almost too much of a coincidence. A disturbing thought crept into my head that the same killer had been aiming for me once again.

The sugar bowl—the woman had asked to borrow the sugar and I had handed her our bowl. Was it possible that someone had poisoned the sugar? The only person who could have done that was Tristram. I shook my head. That was impossible. He hadn’t touched the sugar bowl until he took a lump himself and then offered it to me. He couldn’t have known in advance where we were going because I had been the one that suggested Knightsbridge and chose the coffeehouse. And as far as I knew, Tristram hadn’t been on the boat last Sunday.