A children's tale about a young penguin with an unusual gift and his adventures in Antarctica.

In Emperorland, thousands of emperor penguins are suffering from a shortage of fish to eat. Despite the lean times, they continue to embark upon their main mission in life: to find their mate by singing their individual "heartsong," which expresses their soul. One much-wooed female, Norma Jean, wanders alone until she meets Memphis, the only male whose song inspires her. They, like every other emperor couple, soon produce an egg, after which each father cradles his egg between his legs to incubate it over the long, brutally cold winter, while the mothers leave for the open sea to hunt for fish. Throughout the winter, the males huddle in a large mass, taking turns braving the outer rim and then moving inside the group for warmth. Directed by their venerated leader, Noah, they sing to make their task more palatable and invoke their spirit guides. Memphis, lovesick, envisions Norma Jean and sings passionately, causing him momentarily to lose hold of his egg, which rolls into the freezing snow. Horrified, he snatches it back up and returns to the group. When summer finally returns, the eggs begin to hatch. Memphis has almost given up hope for his still, silent egg when it cracks and two feet emerge. The baby, christened "Mumble" by another new baby, Gloria, soon breaks free of his shell and tap-dances with happiness, causing the other penguins and his father to squirm in discomfort. Soon, the females return, and although Memphis is embarrassed by Mumble's constantly shuffling feet, Norma Jean adores her son without reserve. All of the children attend school led by Miss Viola, who teaches them that without their heartsongs, they cannot be truly penguin. Mumble is entranced with Gloria, who already evidences a lovely singing voice, but when he is called on, his singing is a painful screech. Viola meets with Norma Jean and Memphis, who lies that Mumble's incubation was entirely normal, and Mumble is brought to the special education teacher, Mrs. Astrakhan. She counsels him to summon up his deepest emotions, but when Mumble eagerly tries, his feet unwittingly start tapping, and upon hearing his voice later, Mrs. Astrakhan weeps with despair. Norma Jean pronounces Mumble's dancing cute, but Memphis takes his cues from the other penguins and declares that "it ain't penguin." Over the weeks, Mumble finds isolated areas to dance unobserved, and one day, is set upon by four predatory skua birds. As their boss pins him down, Mumble, hoping to "appeal to his better nature," inquires about the identification tag on his ankle, prompting the skua to wax eloquently on the "aliens," actually humans, who abducted him. When the bird then returns to the task at hand, Mumble flees, eluding his captors by hiding in an ice crevice. Each day at school, he stands silently at the back of the class, and when their education is finished, Noah does not allow Mumble to graduate. Regardless, Norma Jean urges her son to join his peers in their celebration, and he follows them out to their party by the sea. Spotting a few fish nearby, the penguins compete to grab one, and when Mumble succeeds, he gives it to Gloria. When she refuses it, however, a bird snatches the fish from Mumble's mouth, lifting him into the sky and dropping him to the ground with half of the fish intact in his mouth. Gloria, embarrassed, thanks him. That night, Gloria leads the adolescents in a rousing song, but when Mumble sings along, the whole pack complains and demands that he leave. He sleeps alone on an ice floe, waking when a monstrous leopard seal attacks. After a harrowing chase, Mumble escapes by jumping onto the shore, and finds there five Adelie penguins, a smaller, beach-dwelling species. The rambunctious males, whom Mumble dubs the "Amigos," join Mumble in taunting the seal, then admire Mumble's masterly footwork. They invite him back to their colony, where tens of thousands of Adelie males are building nests of pebbles to attract a mate. The Amigos explain that their superior charisma lures the ladies even without a nest, and to prove their claim, they dance Mumble's steps for three females, who respond favorably. Together, the new friends slide on their bellies down steep mountainsides, impressing one another with their daring and finesse. At the tip of the mountain, however, their shenanigans start a mini-avalanche, revealing a huge tractor. Mumble watches with horrified fascination as it sinks into the sea, then calls to the Amigos to help him discern its mysteries. Although the carefree Adelies care little about the tractor, they bring him to their guru, a womanizing charlatan Rockhopper penguin named Lovelace. Lovelace wears a plastic ring from a six-pack that wedged around his neck while swimming one day, which he claims is a "sacred talisman" that allows him to confer with the spirits. After waiting with other worshipful penguins, Mumble asks the mystic if the spirits resemble the aliens of which the boss skua spoke, prompting Lovelace to declare his question-answering over. The Adelies ask Mumble about his soul mate, and when they learn that he cannot sing, hatch a plan to hide behind him while he lip-synchs. When Mumble tries to impress Gloria in this way, however, she quickly uncovers the ruse and chastises him. In desperation, Mumble launches into his most fervent dancing, and Gloria, who has been searching in vain for a mate to complement her forlorn heartsong, is swept away by the beat. Suddenly, her song's true nature is revealed: a jubilant disco celebration. The other young penguins joyfully echo Mumble's dance steps, earning the censure of the elders. Noah demands that they stop, cautioning the colony that the food shortage has been caused by just such "pagan" influences, and that only through strict adherence to rules will the fish return. Although Mumble tries to educate his clan about the "aliens," the true cause of the shortage, they scoff at him. Mumble, unwilling to deny his true self, refuses to stop dancing, and is banished. Knowing the only way back to his family is by discovering the truth about the aliens, Mumble resolves to find them, and visits Lovelace to ask for advice. He and the Amigos find the guru laboring for breath, as the plastic ring has tightened around his neck. Realizing that the ring was not a gift from the gods, Mumble presses Lovelace to lead him to where he found it. To that end, the seven penguins set out across the frozen tundra, and when Gloria follows, determined to be with her true love, Mumble deliberately insults her so she will turn back and not be condemned to life as an outcast. He is heartbroken, but soon must focus on the trek's arduousness. Mumble helps the ailing Lovelace over a mountain, which descends to a herd of huge elephant seals. The vegetarian creatures warn the group that miles away lay the humans, whom they deem the "annihilators." Unafraid, Mumble presses on, sure he can appeal to the humans' better natures. The winds turn torrential, and the penguins struggle forward. Finally, they come upon an abandoned human fishery and spot several more plastic rings floating by the shore. Killer whales attack, catching Lovelace by the ring and tossing him into the air. The motion, however, manages to free him from the ring, and all seven penguins escape to an ice floe, only to see it split apart by a mammoth fishing ship. The penguins scramble to safety, and the sight of more ships inspires Mumble to dive headlong into the sea to confront them directly. Watched with admiration by the others, he braves the dangerous tides, but is borne out to sea and, eventually, washed up ashore in a city. There, he is caught and transported to a zoo, where penguins stand, stunned and despondent, in a glass case with a false "Arctic" backdrop. For days, Mumble tries to talk to the human spectators, but soon loses his voice, and three months later has nearly lost his mind. One day, his stupor is interrupted by a child knocking on the glass rhythmically. In response, Mumble shuffles a few steps, and soon the humans react with excited hysteria. Months later, Mumble returns to Emperorland, an electronic tracking device embedded in his back, and informs the penguins that the humans are causing the food shortage, but dancing charms them. When Noah orders the penguins to sing out against Mumble, the younger set, spurred on by Gloria, instead begin to follow his dance steps. Norma Jean and the Amigos see the commotion and welcome Mumble home, but reveal that Memphis, wracked with guilt for abandoning his son, has lost his heartsong. Mumble appeals to his father to dance, and soon, Memphis revives. Just then, two helicopters land on a rise nearby and humans emerge. Mumble leads his frightened brethren in a line dance, and soon, the delighted humans join in. Within days, footage of the miraculous birds has dispersed throughout the human world, and committees have formed to protect their environment. As the fish begin to replenish, Emperorland is alive with dancing penguins, chief among them Mumble and his bride, Gloria.