There is incomprehensible, and there is inexplicable, and then there is “The Last Airbender,” M. Night Shyamalan’s adaptation of the popular Nickelodeon cartoon “Avatar: The Last Airbender.” Not to be confused with James Cameron’s tale of tree-hugging blue people, this saga revolves around (I think) a war-torn future world waiting for a messiah to unite it.

But the screenplay (also by Shyamalan) is cluttered with so much gobbledygook exposition and confusing action that it’s impossible to grasp what’s supposed to be going on for more than 15 seconds at a time.

The opening scenes introduce us to sister and brother Katara (Nicola Peltz) and Sokka (Jackson Rathbone), two members of Water Nation — one of four nations that were once kept in balance by the mysterious Avatar. But when the Avatar went missing, all hell broke loose, as the Fire Nation declared war on the others, including Air Nation and Earth Nation. Got all that?

Part of the problem here is that Shyamalan has tried to cram about three seasons of the cartoon’s plot points into this one movie, including the story of the prince of Fire Nation (Dev Patel from “Slumdog Millionaire”), who was cast out of the palace for being a wimp. The other, bigger problem is that you don’t care about any of these people, whose motivations and personalities are impossible to discern.

At some point, a savior emerges, Aang (Noah Ringer), a boy who can bend air — i.e., make the wind knock people over — and thus the Avatar who will bring peace to this universe. Sweeping his arms about him and prancing around the set, the bald, wide-eyed Aang spends a dismaying portion of the proceedings looking like he’s practicing tai-chi.

By the time the (mystifying) climax rolls around, the movie has come to resemble an unwieldy hybrid of “Little Buddha” and “Crouching Tiger, Hidden Dragon.”