We Are the Flesh (Tenemos la carne)

After the end of the world, a young brother and sister roam an apocalyptic city looking for food and shelter. They take refuge in the dilapidated lair of a strange hermit who makes them a dangerous offer to survive. He puts them to work building a bizarre cavernous structure, where he acts out his insane and depraved fantasies.

Trapped in a maddening womb-like world under his malign influence, they find themselves sinking into the realms of dark and forbidden behavior.