When half a billion dollars' worth of art vanished

It was the "heist of the century": A two-man team of thieves stole several classic pieces of art from the Isabella Stewart Gardner Museum in Boston, including works by Rembrandt, Vermeer and Manet. More than 25 years later, no arrests have been made and none of the art has been recovered. Erin Moriarty of "48 Hours" tells the tale.