In the wake of a nuclear war, Ann Burden is one of the last surviving humans, eking out a life in a valley that was conveniently spared the ravages of nuclear fallout. After a year of solitude, she is joined by a man named John Loomis, who survived thanks to a suit that he designed before the war. Soon after, they are joined by another survivor named Caleb, and thus begins a complicated love triangle.
Z for Zachariah contains examples of:
- Adam and Eve Plot: Hinted at when John tells Ann they should save up supplies not just for themselves, but also "anyone else". Though she doesn't get what he means, John seems to be thinking they might have a baby some day, and at this point it's left unclear whether anyone else in the world is still alive.
- Adaptational Alternate Ending: The film ends with Ann and Loomis deciding to carry on living together without yet looking for other survivors. In the novel Ann leaves the valley after a tense confrontation between the two.
- Adaptation Expansion: The original novel only had two characters, Ann and Loomis. The film adds a third survivor, Caleb.
- Adaptation Explanation Extrication: The meaning behind the title is omitted from the film.
- The book, however is still shown
- Adaptational Heroism: Loomis is portrayed much more sympathetically in film than he is in the book.
- After the End: The film takes place after a nuclear war has wiped out nearly everyone on Earth.
- Age Lift: Ann is a teenager in the novel, but a grown woman in the film.
- Ambiguous Ending: The ending leaves it deliberately unclear whether Loomis is telling Ann the truth when he claims that Caleb chose to leave the valley to continue his journey, or whether he murdered Caleb and is lying to her to cover it up.
- Bittersweet Ending: If you choose to believe that Loomis is telling the truth about Caleb deciding to leave the valley.
- Downer Ending: If Loomis is lying, then he gets away with killing Caleb, with Ann apparently none the wiser. Having no other alternatives, and despite having stronger feelings for Caleb, she stays with Loomis and the two apparently start a new life together.
- Apocalypse How: Class 4 - life remains undisturbed in the valley in which Ann lives, but it is implied that it has been wiped out on most of the rest of the planet.
- Artistic License – Nuclear Physics: The Movie HandWaves it by saying that the valley is protected by topography and weather patterns, but it is basically impossible for one area to remain completely uncontaminated if the rest of the planet has been irradiated to the point of eliminating all life.
- Canon Foreigner: Caleb does not appear in the novel.
- Despair Event Horizon: Invoked. Ann at one point says that she considered giving up and not planting crops for the next season, but she decided against it.
- Green-Eyed Monster: Definitely in play between Loomis and Caleb, regardless of how you choose to interpret the ending.
- Hazmat Suit: The characters have them, allowing them to venture into irradiated areas outside the valley. One plays an important role in the climax, when Caleb almost slips off a cliff while encumbered by the bulky suit he is wearing, and needs Loomis to save him. Maybe.
- Karma Houdini: If Loomis did kill Caleb, he's this by the end, living with Ann with no more competition, and with her apparently none the wiser of his deeds.
- Last-Name Basis: Caleb always calls John "Mr. Loomis", seemingly in keeping with his Southern civility.
- Love Triangle: Between Ann, Caleb, and Loomis.
- Mercy Kill: John shot a teenager who begged him to, and he thinks this may have been Ann's brother.
- Murder the Hypotenuse: One possible interpretation of the ending, if you believe that Loomis murders Caleb.
- Post-Apocalyptic Dog: Before Loomis shows up, Ann's dog is her only companion.
- Race Lift: Loomis was white in the original book, but is played by Chiwetel Ejiofor in the film.
- Released to Elsewhere: The ending features an ambiguous example. Loomis tells Ann that his romantic rival Caleb has left for a previously mentioned Safe Zone Hope Spot. However, the audience is shown that Caleb had been interested in staying around to romance Ann while expressing doubt that the safe zone is real, right before he ended up hanging from a cliff with Loomis in a position to let him fall or save him. Caleb may have decided to leave after all due to gratitude for Loomis saving his life or fear about how Loomis almost didn't, but it's also possible that Loomis did kill Caleb and is lying to Ann.
- Riddle for the Ages: The end of the movie leaves it ambiguous whether Loomis kills Caleb in a Tragedy Of Impulsiveness by letting go of a rope Caleb is hanging from, or Caleb leaves the valley. Caleb had expressed a desire to stay and be with Ann right before finding his life in Loomis's hands, but might have changed his mind out of gratitude for Loomis saving his life or fear due to how clearly Loomis was tempted to let him fall.
- Sole Surviving Scientist: Loomis is a scientist, and seemingly the only one left alive.
- Spared by the Adaptation: Ann's dog Faro lives, unlike in the book.
- Stab the Scorpion: A variant occurs where the "scorpion" isn't dangerous. Romantic rivals Loomis and Caleb go on a turkey hunt, and Caleb falls several steps behind Loomis and shifts his rifle in the direction of Loomis's back before the two fire at the turkey. However, he really is only shooting at the turkey.
- Take Our Word for It: The devastated landscape outside of the valley is never actually shown, which does little to undermine the descriptions of how barren and ravaged the rest of the world is.
