“There was another thing I kept overlooking,” I went on quickly. “Ray, you kept referring to Onderdonk as a big hulk of a man, and you made it sound as though clouting him over the head was on a par with felling an ox with a single blow. But the man who called himself Onderdonk wasn’t anybody’s idea of a hulk. If anything he was on the slight side. That should have registered, but I guess I wasn’t paying attention. Remember, the first time I ever even heard the name Onderdonk was when the killer came into my bookshop and introduced himself to me. I assumed he was telling the truth, and I took a long time to start questioning that assumption.”

Richard Jacobi scratched his bearded chin. “Don’t keep us in suspense,” he demanded. “If one of us killed Onderdonk, why don’t you tell us who it is?”

“Because there’s a more interesting question to answer first.”

“What’s that?”

“Why did the killer cut Composition with Color out of its frame?”

“Ah, the painting,” said Mordecai Danforth. “I like the idea of discussing the painting, especially in view of the fact that it seems to have been miraculously restored. There it reposes on the wall, a perfect example of Mondrian’s mature style. You’d never know some foul fiend cut it from its stretcher.”

“You wouldn’t, would you?”

“Tell us,” said Danforth. “Why did the killer cut the painting?”

“So everyone would know it had been stolen.”

“I don’t follow you.”

Neither, from the looks on their faces, did most of his fellows. “The killer didn’t just want to steal the painting,” I explained. “He wanted the world to know it was gone. If he just took it, well, who would realize it was missing? Onderdonk lived alone. I suppose he must have had a will, and his worldly goods must go to somebody, but-”

“His heir’s a second cousin in Calgary, Alberta,” Orville Widener cut in. “And now we’re coming to my part of the field. My company underwrote Onderdonk’s insurance and we’re on the hook for $350,000. I gather the painting was stolen so that we’d have to pay, but what we ask in a situation like that is Qui bono? I’m sure you know what that means.”

“Cooey Bono,” Carolyn said. “That was Sonny’s first wife, before he was married to Cher. Right?”

Widener ignored her, which I thought showed character. “To whose good?” he said, translating the Latin himself. “In other words, who benefits? The policy’s payable to Onderdonk, and in the event of his death it becomes part of his estate, and his estate goes to somebody in western Canada.” His eyes narrowed, then turned toward Richard Jacobi. “Or is that Canadian relative actually among those present?”

“He’s in Canada,” Wally Hemphill said, “because I spoke to him at an hour that was equally uncivilized in either time zone. He’s empowered me to look out for his interests in this matter.”

“Indeed,” said Widener.

It was my turn. “The cousin never left Calgary,” I said. “The painting was stolen not for the insurance, considerable though it may be. The painting was stolen for the same reason its owner was murdered. Both acts were committed to conceal a crime.”

“And what crime was that?”

“Well, it’s a long story,” I said, “and I think we should make ourselves comfortable and have a cup of coffee. Now how many of you want cream and sugar? And how many just cream? And how many just sugar? And the rest of you want it all the way black? Fine.”

I don’t think they really wanted coffee, but what I wanted was a breathing spell. When Carolyn and Alison had served the nasty stuff all around the room, I sipped some of mine, made a face, and started in.

“Once upon a time,” I said, “a man named Haig Petrosian had a painting in his dining room. It would later be called Composition with Color, but Petrosian probably didn’t call it anything but ‘My friend Piet’s picture,’ or words to that effect. Whatever he called it, it disappeared around the time of his death. Maybe a family member spirited it away. Maybe a servant made off with it, perhaps acting on the belief that the old man wanted her to have it.”

“Perhaps Haig Petrosian’s son William stole it,” Elspeth Petrosian said, with a sharp glance to her right and another sharp glance at me.

“Perhaps,” I said agreeably. “Whoever took it, it wound up in the possession of a man who found a wonderful way to make money. He bought paintings and gave them away.”

Carolyn said, “That’s a way to make money?”

“It is the way this fellow did it. He would buy a painting by an important artist, a genuine painting, and he would lend it to a show or two in order to establish its provenance and his history as its owner. Then a talented if eccentric artist would be engaged to produce a copy of the painting. The owner would let himself be persuaded to donate the painting to a museum, but in the course of things it would be the copy that wound up getting donated. Farther on down the line, he’d donate the painting to another institution in another part of the country, and once again it would be a copy that changed hands. Occasionally he might vary the pitch by selling the painting to a collector, picking someone who wouldn’t be likely to show it. In the course of a decade, he could sell or donate the same painting five or six times, and if he stuck to abstract artists like Mondrian and had his wacky painter vary the precise design a bit from one canvas to the next, he could get away with it forever.

“And the richer you are to start with, the more profitable it is. Donate a painting appraised at a quarter of a million dollars and you can save yourself over a hundred thousand dollars in taxes. Do that a couple of times and you’ve more than paid for the painting, and you’ve still got the original painting yourself. There’s only one problem.”

“What’s that?” Alison asked.

“Getting caught. Our killer found out that Mr. Danforth was putting together a retrospective exhibit of Piet Mondrian’s works, which in and of itself was no cause for alarm. After all, his fake paintings had survived such exposure in the past. But it seemed that Mr. Danforth was aware that there were far more Mondrians in circulation than Mondrian ever painted. What is it they used to say about Rembrandt? He painted two hundred portraits, of which three hundred are in Europe and five hundred in America.”

“Mondrian’s not been counterfeited on that grand a scale,” Danforth said, “but in the past few years there have been some disconcerting rumors. I decided to combine the retrospective with an exhaustive move to authenticate or denounce every Mondrian I could root out.”

“And toward that end you enlisted the aid of Mr. Lewes.”

“That’s right,” Danforth said, and Lewes nodded.

“Our killer learned as much,” I said, “and he was scared. He knew Onderdonk intended to put his painting in the show, and he wasn’t able to talk him out of it. He couldn’t let on that the painting was a fake, not after he’d sold it to Onderdonk himself, and perhaps Onderdonk began to suspect him. That’s supposition. What was clear was that Onderdonk had to die and the painting had to disappear, and it had to be a matter of record that the damned thing disappeared. All he had to do was frame me for the theft and murder and he was home free. It didn’t matter if the charges stuck. If I went up for the job, fine. If not, that was fine, too. The cops wouldn’t look for someone with a private motive for Onderdonk’s death. They’d just decide I was guilty even if they couldn’t make the charges stick, and they’d let the case go by the boards.”

“And we’d pay the cousin in Calgary $350,000 for a fake painting,” Orville Widener said.

“Which wouldn’t affect the killer one way or the other. His interest was self-preservation, and that’s a pretty good Qui bono six days out of seven.”

Ray said, “Who did it?”