Shortly after midnight on March 18, 1990, two men broke into the Isabella Stewart Gardner Museum in Boston and committed the largest art heist in history. They stole a dozen masterpieces, including one Vermeer, three Rembrandts, and five Degas. But after thousands of leads-and a dollar;5 million reward-none of the paintings have been recovered. Worth as much as dollar;500 million, the missing masterpieces have become one of the nation's most extraordinary unsolved mysteries.