“But surely…” I said.

“No, no,” she said. “I’m not really serious.”

“But is there anyone else you could think of who might want to hurt him or damage his company?” I said.

She pursed her lips and gently shook her head.

“Do you know a man called Komarov?” I asked her.

“Of course,” she replied. “I know Peter very well. He imports polo ponies. But you’re not telling me that he has something to do with what happened to Rolf?”

“I don’t know,” I said. “I just wondered if you had heard of him.”

“He and his wife come and stay with us,” she said in a tone that implied her houseguests were beyond reproach. “They are friends of ours.”

“Lots of people have been murdered by their friends,” I said.

Et tu, Brute?

“When exactly do they stay with you?” I asked her.

“For the polo,” she said.

“At the Lake Country Polo Club?” I asked.

“Yes,” she said. “Rolf is a vice president.”

“Does Rolf have any polo ponies himself?” I asked her.

“Hundreds,” she said. “I wish he would devote as much time to me as he does to his damn polo.” She stopped suddenly and looked blankly out of the window. Life was going to be very different for her from now on.

“Is Peter Komarov anything to do with the polo club?” I asked her.

She turned back to face me. “I don’t think so,” she said. “But I do know that all his horses go there for a few days when they first arrive in the country.”

“Where do the horses originally come from?” I asked.

“South America,” she said. “Argentina, Uruguay and Colombia, mostly, I think.”

“And where do they go after they leave the polo club?” I asked.

“All over the country,” she said. “I have occasionally been to some of the sales with Rolf. You know, at Keeneland, in Kentucky, and at Saratoga.”

I had heard of both of them. They were major bloodstock sales for Thoroughbreds. “So they’re not all polo ponies, then?”

“Oh no,” she said. “I think that most are, but there are definitely some racehorses as well.”

“Why do they all come here first, then,” I said, “to the polo club?”

“I don’t really know,” she said. “But I do know they arrive by plane at O’Hare, or at Milwaukee airport, and then they go to the club by horse van. I’ve seen them being unloaded. Perhaps they need to get over the journey, like jet lag or something. I think they stay for up to a week before being shipped. Except the ones that Rolf keeps himself, of course.” She sighed, and again the tears welled up in her eyes.

“Seems strange to me not to send the racehorses directly to where they’ll be sold,” I said.

“Rolf says they have to be inspected by the vet,” she said. “And he has to do something with the balls.”

“The balls?” I asked.

“Yes,” she said. “The metal balls. They’re something to do with the journey. I don’t really know what, but Rolf always has a big box full of them here a few days after the arrival of each planeload.”

“Do you have any of these balls here at the moment?” I asked.

“I think there are a few in Rolf’s desk,” she said.

She went out of the kitchen and soon returned with a shiny metal ball about the size of a golf ball. She placed it on the counter in front of me and I picked it up. I was expecting it to be heavy, like a large ball bearing, but it was surprisingly light, and hollow.

“What are they for?” I asked her.

“I have no idea,” she said. “But I think they might be also something to do with breeding the ponies.”

“Can I have this one?” I said.

“I don’t think Rolf would be very pleased with me if I let it go,” she replied. “He’s always extremely careful to check he has the right number. He counts them over and over.”

“But it might help me find out why he was injured,” I said.

“Do you really think so?” said Dorothy, again looking so frail and forlorn.

“I don’t know, but it may.”

“Well, I suppose just one will be all right,” she said. “But you must promise to give it back after you have finished with it.”

I promised, and Caroline smiled at her.

WE LEFT the Schumann residence at five to two, having been cajoled by Dorothy into staying for a ham-and-cheese-sandwich lunch. We were late. I swung the Buick back onto I-94 and put its engine to the test. It was a hundred miles to Chicago and Caroline’s rehearsal with the orchestra at four o’clock. And she had to get to the hotel first, to collect her dress for the evening and her beloved viola. It was going to be tight.

“So what do you think this is?” Caroline asked. She sat in the car’s passenger’s seat and tossed the shiny metal ball from hand to hand.

“I have no idea what it’s for,” I said. “But if it has anything to do with Komarov, then I’m interested in finding out.” I accelerated past a huge eighteen-wheeler truck that was thundering along in the center lane.

“Don’t get a speeding ticket,” Caroline instructed.

“But you said…” I tailed off. She had said that her ass would get roasted if she was late.

“I know what I said.” She laughed. “But don’t get stopped or we really will be late.” I eased off the accelerator slightly and the speedometer came back within the limit. Well, it almost did.

“Something to do with polo ponies,” I said. “That’s what Mrs. Schumann said.”

“Perhaps it’s for table polo.” She laughed out loud at her joke. It did look a bit like a metal table-tennis ball, but perhaps it was a fraction bigger than that. “Does it open, I wonder?” she said.

The ball had a slight seam around its equator, and Caroline took the ball in both hands and tried to separate the two halves. She tried to prize it open by pushing her thumbnail in the seam, but without success. She tried to twist one half off the other. In fact, it wasn’t difficult at all, when you knew how. The two halves screwed together with a counterclockwise movement.

I briefly looked at the two hemispheres sitting in Caroline’s hands.

“I’m none the wiser,” I said. “But I do know that it’s not a toy. It’s not easy to make those screw threads on a spherical object as thin as that. Especially one that fits so tightly together. Quite a piece of precision engineering is involved. If Mrs. Schumann is right about Rolf having a big box full of them, then they must have cost a packet to produce.”

“But what are they for?” said Caroline.

“Perhaps they are for putting something in that mustn’t leak out,” I said. “But I don’t know what.”

WE MADE it back to the hotel with five minutes to spare. Caroline grabbed her dress and viola and rushed away with a kiss. “See you later,” she said. “I’ll leave a ticket at the box office.” She skipped out of the hotel and into the waiting bus taking the orchestra to the hall. The door closed behind her and off they went.

I stood in the lobby and felt lonely. Would I ever get used to saying good-bye to her even for just a few hours? While she had rushed off with such excitement at the prospect of rehearsal and then performance, I was left feeling abandoned and jealous. How could I be so green-eyed about a musical instrument? But I shivered at the thought of her wonderful long fingers caressing Viola’s neck and plucking her strings when I wanted Caroline to do it to me. It was irrational, I knew, but it was real nevertheless.

“Pull yourself together,” I said to myself, and went in search of the concierge.

“Lake Country Polo Club?” he repeated, as a question.

“Yes,” I said. “I think it’s near Delafield, in Wisconsin.”

He tapped away on his computer for a while. “Ah,” he said finally, “here it is.”

His printer whirred, and he handed me a sheet of paper with the directions. The club was about five miles nearer to Chicago than Delafield. In fact, we had driven right past it twice today, since according to the directions it sat just off the interstate highway on Silvernail Road. I thanked him, and arranged to keep the rental car for another day.