Plum Creek is a historical novel set in nineteenth-century Texas. It is a coming-of-age story involving Billy McCulloch, a fifteen-year-old boy who accompanies a former Texas Ranger, a black man, and two of his uncles on a quest to rescue a fourteen-year-old girl. The girl was captured by a band of renegades led by a half-breed Comanche killer after they slaughtered the rest of her family in a raid on their home in rural Central Texas.

The pursuit of the renegades is set against a backdrop of post-Civil War Texas, just beginning to recover from the devastation of war and Reconstruction. The character of the former Texas Ranger is loosely based on John Coffee Hays, known as Jack Hays, who was called "Devil Yack" by many Mexican and Native American people because of the fame he won fighting in the Mexican War and, before and after, fighting the Comanches.

As Billy and the older men ride, Texas is emerging into a new age around them. A new social structure is taking hold, the old ways of life are dying, and the future is uncertain.