Jody's earliest memory is of being taken to the town marketplace with his mother whilst an auction that he did not fully understand took place around him. Two men bid feverishly against each other until the auctioneer brought down his hammer and Joey was led away. He had never been apart from his mother before and started crying for her, hearing her cries for him becoming more and more feint as he was taken further away.
Joey's new home was a farm, with a lot of land and a comfortable stable where he was given a stall next to a placid, motherly horse called Zoey. He likes her very much but dislikes the farmer who has purchased him, but forms a deep bond with the farmer's son, Albert, the two becoming soul mates as Albert works hard to transform Joey into a farm horse, his father having threatened to get rid of him unless he can work with Zoey in the fields.
It is the onset of the First World War and heading that the army are buying horses for the front, Albert's father takes Joey to market and sells him to an honorable soldier called Captain Nicholls. Too late Albert rushes to market, but is unable to reverse the sale. He tries to join the army with Joey but is too young so he promises Joey that as soon as he is of age to enlist he will do so, and he will come find him. Captain Nicholls promises to take great care of Joey and also to keep in touch with Albert.
Joey misses Albert and his old life. He makes friends with Topthorne, a beautiful black thoroughbred, and the two are inseparable from that moment on. Joey does not like the man training him; Corporal Samuel Perkins is a former jockey and although an excellent rider he makes up for his short stature by bullying the horses in his care. Captain Nicholls comes to Joey's defense and instructs that he is given more food as he is to be the Captain's horse and should not lose any more conditioning.
The cavalry regiment is eventually sent to France by boat where they will join the front lines. The voyage is rough and both horses and their soldiers are seasick. The mood is one of fevered excitement although once they reach their encampment and the reality of the situation sets in this dissipates. Topthorne, ridden by Captain Stewart, and Joey, ridden by Captain Nicholls, are at the front of the cavalry. The fighting is terrifying and confusing and Joey describes how one moment he can feel Captain Nicholls riding him, the next moment he cannot. Captain Nicholls is killed in the battle.
Joey remains at the head of the cavalry ridden now by Trooper Warren, a kind, gentle las who is not a particularly good horseman but whose conscientious treatment of the horses keeps them going throughout the harshness of the winter. He had a tendency to pray aloud as they rode into battle. Topthorn and Joey lead the regiment over the barbed wire defenses on the battlefield but find themselves in enemy territory as German soldiers appear from the trenches all around them. In an effort to save the remainder of his men from death in battle Captain Stewart orders them to surrender. As he and Trooper Warren are led away in one direction, Joey and Topthorn are led the opposite way. Their German captors respect their bravery and the captain orders his troops to treat them like the heroes they are. They are put to work as stretcher bearers, pulling the ambulance carts. It is work that Joey finds comfort in as it is like the farm work he grew up doing.
The two horses are stables together and one evening are startled by the stable door opening, and a man coming inside with a small girl. Emilie is a sickly child who lives with her grandfather on his farm which has been taken by the Germans as their base camp. Emilie comes to consider the horses her own. Joey is awarded a bloodied Iron Cross medal for bravery by a German soldier they rescue from the battlefield.
After a summer working on the farm for Emilie's grandfather the horses have to leave to follow the German army. Emilie is distraught at the loss of her horses. Topthorn is now ridden by Crazy Friedrich who has become very attached to him. As the horses are drinking from the stream Topthorn stumbles and collapses. Joey realizes he has lost his best friend. As they are mourning him the sound of shells exploding begins around them . Friedrich did not manage to get away and was killed a few paces away from Topthorn. Joey stayed with them for as long as possible, not wanting to be alone in the world, but the gunfire and shelling terrified him and he began to run with no particular direction in mind. He ran all night, stumbling over craters and ditches until he felt barbed wire snag his leg. He ripped himself free but his leg was stiffening and as the sun rose he heard excited voices on both sides of him. Joey had found himself trapped in no-mans land between the British and German trenches.A man in a German uniform waved a white handkerchief came out off the trench on one side, followed by the British soldier on the other. They agree to work together to free Joey then once they have done so they flip a coin to decide who will take ownership of Joey. The British soldier wins and Joey re-joins the British army. The two soldiers observe that if the war was left to them they would be able to solve everything by communicating and trusting each others word.
Joey's leg is extremely painful and he has blood poisoning leading to lockjaw. The huge man in charge of the camp orders that he be washed and tended to; the voice of the soldier answering him sends chills down Joey's spine as he realizes his Albert is the soldier ordered to take care of him. As Albert and his friend David clean the mud from Joey's legs David tells Albert that this horse has the same perfectly equal white sock markings that he has told them his horse from the farm had. Then he washes Joey's forehead and finds the white star marking that Joey had. To confirm that it really is Joey, Albert gives the owl-like whistle that he always used to call Joey; Joey responds by going straight to him. Joey and his commanding officer, Major Martin, nurse Joey back from near death to health.
The end of the war came suddenly and when the men were about to leave for home Albert asked Major Martin what was going to happen to their horses. He learns that they will be auctioned off likely to local butchers who will slaughter them for meat. Major Maerin gives the men every penny if his salary to try to win Joey at auction. They are outbid by the butcher but at the last minute another bid is received and he is sold to Emilie's grandfather. Emilie died after the horses left the farm and he wants to but them and keep them in her memory. When he hears Albert's story he sells him Joey for one penny, as long as Albert promises to keep Emilie's memory alive. Albert does so.
When they arrive home Albert rides Joey into the village and they are welcomes as heroes. Albert subsequently married his sweetheart Maisie but she and Joey never took to each other. Albert's father now doted on Joey like a grandchild and Joey resumed his life as a farm horse alongside his beloved old Zoey.