Vivian Maier was a mystery even to those who knew her. A secretive nanny in the wealthy suburbs of Chicago, she died in 2009 and would have been forgotten. But John Maloof, an amateur historian, uncovered thousands of negatives at a storage locker auction and changed history. Now, Vivian Maier is hailed as one of the greatest 20th Century photographers along with Diane Arbus Robert Frank, Henri Cartier-Bresson and Weegee.