Until just a few years ago, gender dysphoria—severe discomfort in one's biological sex—was vanishingly rare. It was typically found in less than .01 percent of the population, emerged in early childhood, and afflicted males almost exclusively. But today whole groups of female friends in colleges, high schools, and even middle schools across the country are coming out as "transgender." These are girls who had never experienced any discomfort in their biological sex until they heard a coming-out story from a speaker at a school assembly or discovered the internet community of trans "influencers." Unsuspecting parents are awakening to find their daughters in thrall to hip trans YouTube stars and "gender-affirming" educators and therapists who push life-changing interventions on young girls—including medically unnecessary double mastectomies and puberty blockers that can cause permanent infertility.

In this conversation Abigail Shrier recounts how she dug deep into the trans epidemic, talking to the girls, their agonized parents, and the counselors and doctors who enable gender transitions, as well as to "detransitioners"—young women who bitterly regret what they have done to themselves. Coming out as transgender immediately boosts these girls' social status, Shrier finds, but once they take the first steps of transition, it is not easy to walk back. She offers urgently needed advice about how parents can protect their daughters because if this trend continues a generation of girls is at risk.

Abigail Shrier is a writer for the Wall Street Journal. She is a graduate of Columbia College, where she received the Euretta J. Kellett Fellowship; the University of Oxford; and Yale Law School. She lives in Los Angeles, CA.