Most of Walton’s published and unpublished works were originally written in the 1920s through the early 1950s. She worked on her best known work, the Mabinogion tetralogy, during the late 1930s and early 1940s, and her Theseus trilogy during the late 1940s. Once success found her after 1970, she reworked many of her manuscripts for publication over the next twenty years. Walton said of her knack for writing fantasy: “My own method has always been to try to put flesh and blood on the bones of the original myth; I almost never contradict sources, I only add and interpret.” In 1991, she underwent surgery for a brain tumor that proved benign. However, her health continued to decline.