In 1914, a colt named Joey (who narrates this tale) is sold to a drunken farmer. The farmer’s 15-year-old son, Albert, is thrilled. He names and cares for Joey and protects the animal from the farmer’s drunken rages. When the family begins to feel the financial impact of war, Albert’s father secretly sells Joey to an army officer named Captain Nicholls. Albert finds out and begs the captain to let him join the army. Albert is too young, but Nicholls promises to take good care of Joey for him. True to his word, Nicholls treats Joey well and sketches him for Albert.
He is proud of his new horse. Though Joey still fondly remembers Albert, he grows to like his new life and master. He develops a friendship with another horse, Topthorn, who belongs to Nicholls’ friend, Captain Stewart. The horses and men are shipped overseas for battle. Departing the ship in France, the soldiers witness the sorrow and injuries all around them. They soon face their own battle, and Captain Nicholls is killed. A young trooper named Warren becomes Joey’s new owner. Joey and Topthorn do well in battle, but the Germans capture Warren and Stewart and their mounts.
Though the horses no longer have the honor of serving the cavalry, their duties of pulling carts full of wounded German soldiers earn them praise and good care from the men. An old farmer and his granddaughter, Emilie, dote on the horses as well. When the German army moves out of the area, Emilie and her grandfather get to keep the two horses. Joey and Topthorn are content to work the farm until another band of soldiers takes them. They become workhorses under worse conditions than they’ve ever experienced. They grow thin and weak but are nursed back to health in the spring by a man named Friedrich.
Joey is devastated when Topthorn dies of exhaustion and Friedrich dies in battle later that day. Alone and frightened, Joey gets injured on a barbed fence and wanders into “no-man’s-land” between the German and English camps. One man from each side comes out to help him. During the two soldiers’ brief discussion, they realize they are very much alike and that the war might be needless if two people like them could just sit down and talk it out. The English soldier wins the coin toss for Joey and takes him back to camp. Joey is reunited with Albert, who is now an army veterinary orderly. Joey and Albert return home.