Melancholic professor Russell Stone is both entranced and puzzled by the blissful exuberance of a young Algerian student in his Creative Writing course. Russell is deeply curious about, and a little disturbed by Thassadit Amzwar's luminous presence. How can this refugee from perpetual terror be so happy? Won't someone so open and alive come to serious harm?

Wondering how to protect her, Russell researches her war-torn country and skims through popular happiness manuals. Might her condition be hyperthymia? Hypomania? Russell’s amateur inquiries lead him to college counselor Candace Weld, who also falls under Thassa’s spell. Dubbed Miss Generosity by her classmates, Thassa’s joyful personality comes to the attention of the notorious geneticist and advocate for genomic enhancement, Thomas Kurton, whose research leads him to announce the genotype for happiness.

Russell and Candace, now lovers, fail to protect Thassa from the growing media circus. Thassa’s congenital optimism is soon severely tested. Devoured by the public as a living prophecy, her genetic secret will transform both Russell and Kurton, as well as the country at large.

What will happen to life when science identifies the genetic basis of happiness? Who will own the patent? Do we dare revise our own temperaments? In his most exuberant book yet, Richard Powers asks us to consider the big questions facing humankind as we begin to rewrite our own existence.