After the Second Civil War—which isn't between the North and the South, or even between Katy Perry fans and Taylor Swift fans—the Bill of Life is drafted, a bill that outlaws abortion, but makes it legal to "retroactively 'abort' a child" between the ages of 13 and 18. The process is called unwinding. It's a sci-fi procedure that chops up a kid the way McDonald's dices chicken parts, and donates all these parts to science, pink slime and all.
Unwind begins as our three heroes (well, two heroes and an antihero), Connor, Risa, and Lev—all of whom are due to be unwound for one reason or another—manage to escape and end up on the run. Their plan goes well until Lev, who wants to be unwound, turns the group in, splitting them up. Connor and Risa end up in an Underground Railroad of sorts, run by a retired Admiral and an ancient antique shop owner, that ships kids to an airplane graveyard in the desert, while Lev teams up with a boy nicknamed CyFi, who is in search of secrets of his past.
In the Graveyard, Connor and Risa work for the Admiral, while their rival, a fellow unwind on the run named Roland, plots against them. There's a murder mystery, an abandoned Air Force One, and more cafeteria dining scenes than a chapter of Twilight. Lev arrives, bodies are dug up in the desert, and a strange cult of chaos is plotting…something. Before you know it, the kids are revolting, Air Force One is set on fire, and Connor and Risa are forced to team up with Roland to save the Admiral's life.
Roland, who learned to fly a helicopter in a very short period of time, flies them to a nearby hospital…and then promptly turns them all in to the police. This backfires, as all three of them are shipped to the Happy Jack Harvest Camp to be unwound. Uh-oh. Lev shows up—again—but this time he's part of that strange chaos cult known as the Clappers, a group of suicide bombers who inject explosives into the bloodstream and blow themselves up by clapping.
After Roland is unwound, Connor is next. Lev's companions blow up the unwind facility to save Connor, but end up critically injuring him and Risa by mistake. Lev decides not to clap himself to death and decides to save Connor and Risa instead. Lev, the Clapper who didn't clap, escapes unwinding by being thrown in jail shortly after this incident. Risa escapes unwinding by ending up with a spinal cord injury so bad she can't walk. And Connor escapes unwinding by finding a fake ID and managing to pass himself off as an older guard.
Even though Connor loses his arm, and his limb is replaced by Roland's (tacky tattoo and all), Connor holds his head up high—and at least it's his own head—and returns to the Graveyard, where he attempts to calm things down and organize the remaining kids there to start a revolution.