“In the early seventies, right before I met you, I was in Paris on business. I had a few hours to kill between appointments and decided to look up Isaac Weinberg. I went to the address in the Marais that was listed in my father’s notebooks, but Weinberg wasn’t there. He hadn’t survived the war. But I met his son, Marc, and told him about the entry in my father’s notes. He denied the story at first, but finally relented and allowed me to see the painting after swearing me to eternal secrecy. It was hanging in his daughter’s bedroom. I asked whether he might be interested in parting with it. He refused, of course.”

“You’re certain it’s Vincent?”

“Without a doubt.”

“And you haven’t been back since?”

“Monsieur Weinberg made it quite clear the painting would never be for sale. I didn’t see the point.” Isherwood stopped walking and turned to face Gabriel. “All right, petal. I’ve told you the story. Now suppose you tell me what this is all about.”

“I need that van Gogh, Julian.”

“Whatever for?”

Gabriel took Isherwood’s sleeve and led him toward the door of the gallery.

THERE WAS an intercom panel next to the glass door, with four buttons and four corresponding nameplates. One read: ISHER OO FINE AR S: BY APPOINTMENT ONLY. Isherwood opened the door with a key and led Gabriel up a flight of stairs covered in a threadbare brown carpet. On the landing were two more doors. To the left was a melancholy little travel agency. The owner, a spinster named Miss Archer, was seated at her desk beneath a poster of a happy couple splashing in azure water. Isherwood’s door was on the right. His latest secretary, an apologetic-looking creature named Tanya, glanced up furtively as Isherwood and Gabriel came inside. “This is Mr. Klein,” said Isherwood. “He’d like to have a look at something upstairs. No interruptions, please. That’s a good girl, Tanya darling.”

They entered a lift the size of a phone booth and rode it upward, standing so close to one another that Gabriel could smell last night’s claret on Isherwood’s breath. A few seconds later the lift shuddered to a stop and the door opened with a groan. Isherwood’s exposition room was in semidarkness, illuminated only by the mid-morning sun filtering through the skylight. Isherwood settled himself on the velvet-covered divan in the center of the room while Gabriel led himself on a slow tour. The paintings were nearly invisible in the deep shadows, but he knew them well: a Venus by Luini, a nativity by Perino del Vaga, a baptism of Christ by Bordone, a luminous landscape by Claude.