IT'S THE END of the world as we know it, and things aren't fine: Sheltered from radioactive fallout by the unique geography of a rural valley, Ann (Margot Robbie) might be the last woman on Earth. It's a lonely and sad life—one haunted by Ann's memories of her family, and one threatened by the difficulty of subsisting off of the land. And Ann's life only gets stranger when another survivor, John (Chiwetel Ejiofor), happens upon the valley. Despite being a scientist, John immediately strips off his hazmat suit and jumps under a waterfall, then immediately starts vomiting from radiation poisoning; Ann nurses him back to health, unaware that things are about to get even stranger. Because then another survivor, Caleb (Chris Pine), shows up, and what used to be a quiet life on a farm is a post-apocalyptic Three's Company. Except it's two guys and one woman, and the woman looks like Margot Robbie.

Very loosely adapted from the 1974 novel by Robert C. O'Brien, (the same guy who wrote Mrs. Frisby and the Rats of NIMH!) Z for Zachariah takes a few pages from the Twilight playbook: One would think that this would be Ann's story—a story about her decisions, her losses, and her ways of moving forward—but instead, Z turns into a pissing contest between John and Caleb over who gets to bone Ann. That's too bad, because director Craig Zobel has a great eye for the post-human landscapes the story provides, and one would be hard-pressed to think of three better actors to watch play off each other. Ejiofor, as ever, is great, Pine offers welcome range beyond the rakish charm of James T. Kirk, and Robbie, coming off her fantastic turn in The Wolf of Wall Street, cements her status as one of Hollywood's best up-and-coming actors.

But here, all three are working from thin cloth; by the eighth or ninth time the camera holds on John glowering at Caleb, or the 10th scene where Ann's entire purpose is to look distraught, one senses these actors' talents aren't being fully utilized. Time to dig up an old paperback of O'Brien's book.