Yet Maier was clearly fascinated by people — and by the little, quirky details that individualized them. She took her camera everywhere and didn’t miss a beat, capturing spontaneous moments of street life and wonderful, candid portraits of people she saw. At times she was underhand, sneaking an image; at other times she would befriend her subjects and collaborate with them. Either way, she was relentless in getting what she wanted, and her images form an indelible portrait of 1950s-era Chicago.

Almost as obsessive as Maier, Maloof goes on an odyssey to discover the woman behind the images, interviewing Maier’s grown-up charges and employers, who include the talk show host Phil Donahue. Acutely conscious of how private and secretive Maier was, Maloof admits he “can’t help feeling a little uncomfortable or guilty, exposing the work of someone who didn’t want to be exposed.” Yet he concludes that the work is too important to bury — and so Maier joins the ranks of artists like Franz Kafka and Emily Dickinson, finding a level of celebrity in death that they never craved in life.

The big question, of course, is, why? Why did Maier keep her images hidden, not even trying to sell them when she was poor and dying? “Had she made herself known, she would have become a famous photographer,” says celebrated photographer Mary Ellen Mark.