The story of psychologist William Moulton Marston, and his polyamorous relationship with his wife and their mistress who would inspire his creation of the superheroine, Wonder Woman.

Details the unconventional life of Dr. William Marston, the Harvard psychologist and inventor who helped invent the modern lie detector test and created Wonder Woman in 1941. Marston was in a polyamorous relationship with his wife Elizabeth, a psychologist and inventor in her own right, and Olive Byrne, a former student who became an academic. This relationship was key to the creation of Wonder Woman, as Elizabeth and Olive's feminist ideals were ingrained in the character from her creation. Marston died of skin cancer in 1947, but Elizabeth and Olive remained a couple and raised their and Marston's children together. The film is said to focus on how Marston dealt with the controversy surrounding Wonder Woman's creation.

The story is told in flashbacks set during a 1945 testimony that William Moulton Marston gives to representatives of the Child Study Association of America. In the year 1928, William and his wife Elizabeth teach and work on their research at the associated Harvard and Radcliffe Colleges. One day, William hires one of his students, Olive Byrne (daughter of Ethel Byrne and niece of Margaret Sanger - two famous suffragists and feminists of the 20th century) as a research assistant. Olive aids in the Marstons' work in inventing the lie detector and conducting research on William's DISC theory on human interactions, and the three soon grow close. One after another tests by the lie detector reveal that they have fallen in love with one another, and all three of them begin to engage in a poly-amorous relationship.