The past weighs heavily on the present in "Post Tenebras Lux," the haunting, hallucinatory jigsaw puzzle that earned Mexico's Carlos Reygadas the 2012 Cannes best director's prize. The otherworldly drama shuffles decades in its characters' lives, flits between images of nature-documentary clarity and breathtaking surrealism, following an associative logic all its own.

The film is shot in a boxy format, the margins of the image usually rippled and faded, as if the action was a darting memory to be hatched before it fades.

The film's framework is a psychological portrait of an affluent Mexican couple who move to the countryside with a toddler son and daughter. They seek their place in this teeming landscape, a spectacular vastness neither benevolent nor malevolent, merely indifferent to their existence. Their human encounters are a friction of class conflict and domestic strife. There are also moments of warm fellowship and family solidarity.

The film has no more plot than a symphony, but its themes are dramatic and somber. The title (light after darkness, in Latin, a phrase historically linked to the Protestant Reformation) offers hints, as do the film's episodes of loss and redemption.

Juan (Adolfo Jimenez Castro) and Natalia (Nathalia Acevedo) are an urbane couple with half-hidden vices. Outwardly calm, he has an explosive temper, savagely attacking one of their dogs. She has unruly passions of her own. In a nudist steambath/swingers' club, she copulates with a stranger while a maternal woman holds her in imitation of Michelangelo's "Pietà."

Sin and salvation are much on Reygadas' mind. In two dreamlike sequences, a horned humanoid demon, glowing neon red, walks through the sleeping's family's house, observed only by the little boy.

Obscurity duels with illumination. Characters with silly nicknames like R2D2, Toad, Glove and Seven turn out to be not so laughable after all. There are enigmatic rugby sequences shot at an English boarding school. When Juan is bedridden following an assault, Natalia serenades him with a Neil Young's "It's a Dream."

The film climaxes with a bizarre image of body horror suggesting that it's all been in Juan's head. At times it's a lyrical fantasy, at others an intensely visceral nightmare, one of the oddest and certainly one of the boldest films in years.