Rosemary Sutcliff 
Changeling 

Tethra is not like the other children in his village. Fourteen years ago, he was left on the banks of a river, swapped by the Hill Folk for a human woman’s child, replacing the seventh son of Conan. Murna chose to raise him as her own, despite the dire warnings of their village leader.Raising a child of the Hill Folk will bring disaster upon the Epidii people.The dark days have arrived, bringing a poor harvest, a winter of plagues, and unsuccessful hunts. The Old One once again rallies the clan to cast Tethra out, this time with support turning against Tethra and Conan. To spare his father, Tethra runs away, and stumbles across some members of the Hill Folk, his own people, who take him in.As Tethra lives among them, however, he must decide if he is truly one of them, as his blood suggests, or if instead his real place is with the Epidii.