A botched circumcision on an infant, David Reimer, is followed by a "sex reassignment" surgery. The decision is shaped by John Money's theories on "optimal" gender and gender identity formation.

Money, along with the parents, decide that David would be happier as a "girl." Female genitalia is surgically created for David, who will be given hormone therapy throughout his adolescence. Reimer will not be told until much later what happened to him as an infant, nor that Money is tracking Reimer's life as a test case to determine the success of "sex reassignment."

As an adult, Reimer will identify as male and struggle with depression and gender dysphoria (the sense that one's body does not match one's internal experience of gender) and will end his own life in his late 30s.

David Reimer's case will become known as the "John/Joan case" and Money will claim it publicly as a success that supports early interventions of "sexual assignment" of the bodies of intersex infants.