Mary L. Trump, born May 1965, a clinical psychologist, is the oldest child of Fred Trump Jr., and the oldest grandchild of Fred Trump Sr. Mary's father died in 1981 at the age of 42 from a heart attack due to alcoholism.

In this revelatory, authoritative portrait of Donald J. Trump and the toxic family that made him, Mary L. Trump, a trained clinical psychologist and Donald’s only niece, shines a bright light on the dark history of their family in order to explain how her uncle became the man who now threatens the world’s health, economic security, and social fabric.