A boy comes to a dark, desolate corner of town called "the Street of the Lifted Lorax," to learn who the Lorax was and how he got "lifted and taken away." Through a "whisper-ma-phone," the Once-ler tells the boy what happened. When the Once-ler first arrived at this place, it was a beautiful, sunny forest where the Swomee-Swans sang, the Humming-Fish hummed, and Brown Bar-ba-loots played in the shade while eating the fruit of the Truffula Trees, colorful woolly trees spread throughout the area. Enchanted by these gorgeous trees, the Once-ler built a small shop, where he chopped down a tree and knitted a Thneed, an odd-looking but versatile garment that he insisted "everyone needs." Out of the stump popped a strange little man called the Lorax, who claimed to "speak for the trees." The Lorax first pooh-poohed the Once-ler's creation, until someone came along and bought it. Spurred by greed, the Once-ler invited all his relatives to town where they started a huge Thneed-making business, chopping down Truffula Trees left and right, much to the Lorax's distress. The skies gradually got darker and more polluted, forcing the Lorax to send the Bar-ba-loots, the swans, and the fish off in search of a better place to live. The Once-ler, while upset to see the animals go, dismissed the Lorax's pleadings until the last Truffula Tree got chopped down, leaving the Once-ler alone with the Lorax and a failed business in a desolate place under a dark smoggy sky. With a "sad backward glance," the Lorax picked himself up by the "seat of his pants" and floated away through a hole in the smog. At the end of the story, the Once-ler reveals that he has one last Truffula seed left, and instructs the boy to start a new forest so that "the Lorax and all of his friends may come back."

-- Wikipedia: http://en.wikipedia.org/wiki/The_Lorax