"IF YOU DANCE THIS WALTZ, YOU'LL MARRY MY SON..."" The millionaire mocked, but the black maid was a dancing champion. The marble gleamed in the light from the crystal chandeliers, reflecting the luxury and power of Manhattan's elite gathered in the main lobby of the new Thompson Holdings tower. It was the most anticipated opening of the year: two hundred guests, all wealthy, influential, accustomed to the world revolving around them. Between glasses of champagne and muted laughter, the evening u