A small miracle of a movie, this unassuming indie feature, which develops a 2008 short film by the same writer-director, won an audience award at SXSW in Austin last year. And it's not hard to see what towed their hearts away.
It's impossible to resist the unforced authenticity of the performances, particularly from Larson. Her character, Grace, heads up the frontline counselling team at a halfway house-cum-foster home for troubled teens (the unit gives the film its awkward title).
Cretton, whose script is a marvel of restraint and precision, eases us slowly into his characters' worlds, introducing a cast of characters that shrug off stereotype.
It comes as no surprise that Grace, who is in a tentative relationship with a colleague Mason (Gallagher), has a traumatic back story of her own. But it is deftly woven into the wider narrative involving an abused girl whose cause Grace adopts.
This summary makes the film sound bleak but it's far from a downer; if anything, the teens' predicaments are slightly sanitised and the ending is a trifle glib.
But all the characters are ones you care about - even love - almost as soon as you lay eyes on them. That is some achievement. Recommended.
Brie Larson, John Gallagher jun, Kaitlyn Dever, Rami Malek, Keith Stanfield
M (offensive language)
Small and perfectly formed