Wringer explores the theme of peer pressure. Palmer LaRue is anxious about his upcoming tenth birthday. In his town, the annual Family Fest serves as a fundraiser and concludes with a pigeon shoot, where participants shoot five thousand live pigeons. Boys who are ten years old become "wringers," tasked with breaking the necks of injured pigeons. Palmer is appalled by the event, yet for years he convinces himself that the pigeons are better off this way. He and his friend, Dorothy Gruzik, avoid the pigeon shoot by either playing on the swings far from the shooting field or staying away from the park entirely on that day. As Palmer's tenth birthday nears, he desires to join a gang led by Beans, whose sole ambition since age four has been to become a wringer.

Palmer gains entry into the gang and is given the nickname "Snots." He begins to participate in their bullying of his former friend, Dorothy. Despite this, his fear of turning ten does not diminish. Then, much like the albatross in "The Rime of the Ancient Mariner," a pigeon taps on Palmer's bedroom window. He attempts to scare it off, but when he opens the window, "Nipper" enters his room, and Palmer becomes the bird's guardian.

Complicating matters, the gang discovers Palmer is hiding a pigeon. Palmer must devise strategies to distract them, and the stress of keeping Nipper a secret from both his parents and Beans nearly overwhelms him. Eventually, Palmer apologizes to Dorothy and confides in her. She takes Nipper with her on a family trip to the beach to release him and ensure his safety, but unknowingly lets him go in an area where pigeons are captured for the shoot.

The situation builds to a dramatic climax. Palmer turns ten, and the day of the pigeon shoot arrives. Palmer refuses to attend, but an unseen force compels him to the shooting field. He watches in horrified fascination as pigeons are released and either killed or wounded. He cannot look away as ten-year-old boys race onto the field to break the necks of injured birds. Dorothy joins Palmer and reveals that she released Nipper in the city at the railroad yards instead of at the ocean. Alarmed, Palmer realizes that the trusting Nipper is in one of the crates of pigeons waiting to be released. Desperately, he searches the silent crates for Nipper. All the birds look alike, but after what feels like hours, a bird steps out of a crate rather than flying. The shooter misses, and the bird takes to the air, but instead of flying to freedom, it circles and begins to descend. It's Nipper. How can Palmer save his friend?