In the spring of 1974, Calliope Stephanides, a student at a girl's school in Grosse Pointe, Michigan, finds herself drawn to a chain-smoking, strawberry-blonde classmate with a gift for acting. The passion that furtively develops between them, as well as Callie's failure to develop, leads Callie to suspect that she is not like other girls. In fact, she is not a girl at all; due to a rare genetic mutation Callie is part girl, part boy.