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 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 polyamorous relationship.
As word about their unconventional relationship gets out, the Marstons are fired from the university. Olive reveals that she is pregnant and moves in with the Marstons shortly after. The trio decides to build a family together and create a fabrication to keep secret the nature of their relationship.
The family settles in a New York suburb, happily together. By 1934, both Elizabeth and Olive bear children by William (Olive has two sons and Elizabeth has one son and one daughter), telling the neighbors that Olive is a widow and taken in by the Marstons. William starts trying to make a living as an author. Elizabeth takes a job as a secretary and becomes the main breadwinner of the family. Olive stays at home and takes care of the kids, occasionally submitting her writing samples to publishers. They raise their four children together, and Elizabeth names her daughter after Olive.