Mexican novelist, screenwriter and occasional director Guillermo Arriaga made his name in the film realm penning multi-threaded dramas about the ripple effects of tragic incidents. “Amores Perros” and “Babel” stand out among them. Now the scribe’s cinematic legacy turns into a family affair with his children Mariana and Santiago Arriaga making their feature directorial debut via a searing coming-of-age road trip movie their father wrote.

But don’t expect the breezy sexiness of something like Alfonso Cuarón’s “Y Tu Mamá También.” Despite featuring adolescent protagonists, this journey into maturity holds major emotional stakes but few flutters of careless abandon. As is common in Arriaga’s scripts, the tale finds its potency in the intricate moral grays of the human condition, here portrayed through a collection of strikingly incisive performances by the young cast.

Set in early 1990s Mexico, “Upon Open Sky” begins on an empty desert highway. Twelve-year-old...