The four series follow Grace Harlowe and her friends through high school, college, abroad during World War I, and on adventures around America. In The High School Girls Series, Grace attends Oakdale High School with friends Anne Pierson, Nora O'Malley, and Jessica Bright. The four promote fair play and virtue while winning over troubled girls like Miriam Nesbit and Eleanor Savell, playing basketball, and founding sorority Phi Sigma Tau. The group becomes friends with boys in their acquaintance: David Nesbit, Tom Gray, Hippy Wingate, and Reddy Brooks, forming "The Eight Originals." The College Girls Series sees the friends part ways: Grace, Anne, and Miriam depart for Overton College, while Jessica and Nora attend a conservatory. The Eight Originals gather on holidays, but the seven College books focus on the three at Overton, along with new friends like J. Elfreda Briggs. They form Semper Fidelis, a society devoted to aiding less fortunate students at Overton. Following graduation, Grace rebuffs offers of marriage for "what she had firmly believed to be her destined work," managing Harlowe House at Overton. By the end of the series, she and most of her friends have married within their circle. Grace Harlowe Overseas Series follows Grace and many of her friends to Europe to serve in World War I. A number of the college friends join a Red Cross unit known as the Overton Unit, but as the war progresses, they grow more scattered. At one point, the remaining principal characters consist of Grace and J. Elfreda, while the rest fall to the periphery. Grace and her husband return with a daughter, Yvonne, whom they adopted in France. Grace Harlowe Overland Riders Series follows Grace and some of her friends through adventures on horseback around North America, upon their return from Europe.