Featuring Vivian Maier. Rated PG.

Vivian Maier lived her life in boxes—mostly in the cramped back rooms of other people’s families, for whom she worked as a less-than-lovable nanny. No Sound of Music followed from her child-minding sojourn in the Chicago suburbs. But Maier’s true personhood was expressed most fully through the box camera hung around her neck everywhere she went.

So it’s not entirely surprising that Maier, who died penniless in 2009, was rediscovered in boxes—that is, in carton after carton of prints, negatives, and undeveloped film squirreled away and unclaimed by their owner. These truckloads were bought at auction, mostly sight-unseen, by curator and now filmmaker John Maloof, who became the sole copyright owner of the 100,000 or so images she left behind. This presents a dilemma for Finding Vivian Maier, which is both an act of shameless promotion and a sincere excavation of an artist who hid her work, and herself, while still alive.

Codirected by Maloof and Bowling for Columbine producer Charlie Siskel, this fascinating doc offers talking-head testimonials to the validity of Maier’s work, with the likes of Mary Ellen Mark and Joel Meyerowitz pointing out the keen perception behind her street photography, which could be as creepily acidic as anything by Weegee or Diane Arbus but also as humanly embracing as Fred Herzog and Garry Winogrand—especially when it came to the underdocumented African-American denizens of Chicago, New York, and other places she travelled.

As with Winogrand, who left behind troves of uncurated images, questions about artistic intentions are important, although these are concerns that Maloof finds inconvenient. Still, it’s genuinely engaging to follow his methodical digs into her work and life, mostly revealed by the now-middle-aged children she cared for—even if that’s too warm a phrase for this darkly introspective eccentric of uncertain sexuality and provenance.

The tall, angular recluse (a ringer for The Beverley Hillbillies’ Miss Hathaway) was born in France to French and Austrian parents, and she changed her history and accent to fit different situations. The real reasons this protean creator refused to share her art are now permanently buried. But viewers can’t be blamed for wanting to peek inside such a mysterious coffer.