The protagonist of the novel, Leisha Camden is among the first 20-or-so individuals to receive the genemod for Sleeplessness. Born in 2008 to the rich entrepreneur Roger Camden and his wife Elizabeth, Leisha is bred to be tall, slender, and blonde. She also has a non-genetically modified twin sister Alice with whom she has a fraught relationship for much of the book. Leisha's character is most frequently defined in philosophical terms, and the arc of her personal philosophy's evolution and maturation makes up the book's consistent narrative through-line.

For example, Leisha’s father indoctrinates her from an early age to embrace Yagaiism, a philosophy modeled after Ayn Rand's Objectivism that prizes individual achievement and rational thought above all else. A rebuke of communism, Yagaiism is based on mutually beneficial trade and opposes any institution that coerces individuals to trade the fruits of their achievements to help the needy. While Leisha's intellectual and economic privilege initially blind her to any other system of thought, she soon integrates components of other philosophies into her worldview, particularly those of Enlightenment philosophers like John Locke and Jean-Jacques Rousseau, who prized tacit social contracts that help maintain order and a measure of equality.