The 30 or so guests enjoying spring rolls and white wine were gathered in a small third-floor gallery at the Metropolitan Museum of Art to celebrate Subhash Kapoor, a convivial Manhattan art dealer who had donated 58 miniature drawings of Indian aristocrats, deities and beasts.

On this spring evening in 2009, Mr. Kapoor, 60, owner of Art of the Past on Madison Avenue, stood atop the Indian art world. After his 35 years in business, museums and collectors were paying seven figures for his Hindu, Buddhist and South Asian antiquities. A 900-year-old dancing Shiva went to the National Gallery of Australia, a thousand-year-old bronze Ganesha to the Toledo Museum of Art in Ohio. Now, he was being toasted by the Met for a gift of artworks from his homeland.

“He had become quite a big fish, and he seemed thrilled,” said Eleanor Abraham, a fellow gallery owner in the crowd that night.

What no one in the room knew was that Mr. Kapoor was under investigation on two continents, suspected of running a $100 million art smuggling operation.