Who is Ruth Starbuck from Jailbird and what is their importance?

Ruth is described by Starbuck as one of the four women he ever loved. The other three are Mary Kathleen O'Looney and Sarah Wyatt (see below) and his mother (see above). Ruth is a survivor of a Holocaust concentration camp, discovered by Starbuck while on a diplomatic assignment in postwar Germany - because of her skill with languages, Ruth is acting as a freelance interpreter. Starbuck immediately becomes attracted to her, hires her, courts her, and eventually asks her to marry him. After having discovered firsthand (in the concentration camp) just how inhumane both the world and the people who populate it can be, Ruth considers both love and marriage essentially futile, but lets herself be persuaded by Starbuck to let him love her, to marry and to have a child.