What it's all about
I know there is great debate over Billy's involvement, over the "actors" and their specific motivations. However the bottom line is simple. Love. The "Oldman" loved all his women (paintings), he never loved a real woman, let alone had intimate contact with a woman. The young girl whispered that she would always love him, no matter what, and her unseen face showed strong sincerity. Oldman was going to the police, had had enough pieces of evidence to have the perps found. He then recalled making love. He really did love a woman and for that moment she loved him back. He no longer loved pieces of canvas and paint. The young girl was actress who played an extreme shut-in. Oldman was the real shut-in, in his heart. I speculate that in the end, at the table, he was not alone. After 60+ years of dry shallow empty love, he had the beautiful memories of a real life love, if not for only one time. His paintings meant nothing to him now.