Something is wrong with Billie Weinstein's older sister, Cassie, now in her first year at Cornell. She has given away all her clothes except an old sweatsuit and blue jeans. She studies obsessively, convinced she's failing despite a stellar academic record. She rescues food and paper products from the garbage, unable to bear seeing anything wasted. And she's losing weight dramatically.

Even though their father is a doctor, it takes the family several months to recognize and acknowledge all the classic symptoms of anorexia and get Cassie to a psychiatric hospital. In the meantime Billie, still in high school, divides her energies between worrying about her sister, coping with an overbearing father, and finding her way in a relationship confused by sexual pressures and ethnic differences.

Her best friend's large, close, messy, jovial Italian family offers her a refuge from her own much less expressive one, but she discovers they have their own stresses, mostly financial, which drive them suddenly out of town in a moment of crisis. So it's a year of loss, transition, and rapid maturing for Billie, who finds, when her sister comes home with an uncertain prognosis, that she can no longer be the "baby," but has assumed a new, more responsible place in the family system and a new authority over her own life, defined in terms that have less to do with her sister, and more with her own desires and purposes.