This is the long-neglected story of a literary marriage and the wife who helped America's first canonical playwright launch his career. Biographers of Eugene O'Neill have been quick to label his marriage to actress Carlotta Monterey as the defining relationship of his illustrious career. In doing so, they overlook the woman whom Monterey replaced - Agnes Boulton, O'Neill's wife of over a decade and mother to two of his children. O'Neill and Boulton were wed in 1918 - a time when he was still a little-known writer of one-act plays and she a successful pulp novelist - and it was during their marriage that O'Neill would rise to become America's foremost playwright. By exploring the configuration of their marriage, William Davies King unlocks fresh insights into the plays written during this fruitful period. Drawing on more than sixty published and unpublished writings by Boulton, including her 1958 memoir ""Part of a Long Story"" and an extensive correspondence, the book reveals the clues that a marriage might hold to literary history.