In 1912, a young boy named Albert Narracott (played by Jeremy Irvine) hails from Devon, England, where he experiences the awe-inspiring moment of a Bay Thoroughbred foal’s birth. As Joey grows, Albert finds joy in watching the colt gallop through the luscious fields alongside his mother. However, complications arise when his father, Ted (portrayed by Peter Mullan), defies his wife’s wishes—Rose (played by Emily Watson)—and purchases the horse at an auction, driven by a desire to assert his pride over their landlord, Mr. Lyons (acted by David Thewlis). Despite a friend’s warnings about a more suitable plow horse, Ted’s determination to outbid others leads to the acquisition of Joey at a steep cost of 30 guineas (31½ pounds), leaving him unable to pay rent.

As tensions escalate, with Mr. Lyons poised to take over the farm if the rent is not settled by autumn, Ted concocts a plan that includes cultivating a challenging tough-field for turnips. Meanwhile, young Albert devotes countless hours to training Joey, fostering a deep bond with him in the process. His best friend, Andrew Easton (played by Matt Milne), is there as Albert teaches Joey various commands, even using owl calls to signal him.

However, the strain of war hangs over the Narracott family, particularly as Ted grapples with his traumatic past from the Second Boer War, where he earned a Distinguished Conduct Medal. Although he and Rose retain Ted’s war medals and regimental pennant, significant tension remains as Rose reveals that Ted has little pride in his military service, having hidden his medals.

As the war ignites, the pressures mount. Ted, unable to sustain the burden of the farm, makes the painful decision to sell Joey to the young cavalry officer Captain James Nicholls (played by Tom Hiddleston). During an emotional farewell, Albert implores the captain to care for Joey, but the officer can only assure him of his intent to return the horse after the war. In a heart-wrenching gesture, Albert ties his father’s pennant to Joey’s bridle before the horse is taken away.

Joey soon finds himself transformed into a military horse, forming a bond with another horse named Topthorn as they prepare for the harsh realities of combat. Their deployment in France starkly emphasizes the grim fate that awaits cavalry units, manifesting tragically as Captain Nicholls and his troops face a brutal ambush leading to devastating losses, including Nicholls himself.

As time passes, Joey and Topthorn endure grueling service under the German army, where their resilience is tested daily. They are eventually discovered by a 14-year-old German boy, Michael (depicted by Leonard Carow), who sees potential in the horses to pull an ambulance. However, the brothers’ mission to escape to Italy ends tragically as they are executed by their own forces.

In a poignant twist, a young French girl named Emilie (played by Celine Buckens), who lives with her grandfather (portrayed by Niels Arestrup), takes refuge in caring for Joey and Topthorn after finding them. She cleverly hides the horses from German soldiers, but tension escalates when soldiers raid the farm, ultimately resulting in the horses being seized again, with Emilie’s grandfather clinging to the cherished pennant.

As the war progresses, Joey experiences grave hardships pulling heavy artillery, leading to the tragic death of Topthorn. Meanwhile, Albert joins the fight, desperately searching for his beloved horse amid the chaos of the Second Battle of the Somme. In a gripping series of events, Joey escapes, drifts through no-man’s land, and is rescued by soldiers from both sides, showcasing a rare moment of solidarity amidst war.

When Albert’s path intersects with Joey’s once more, now in a medical camp, a heartwarming reunion unfolds as he calls out to his horse using the familiar owl call. Despite Joey’s injuries, their bond transcends the bleakness of war, and the muddy coverings revealing Joey’s markings add to the emotional intensity of their reunion.

With the war’s end marked by the armistice on the 11th hour of the 11th day of the 11th month in 1918, Albert fights for the opportunity to bring Joey home, culminating in a dramatic auction where hope and determination collide. Assisted by funds from fellow soldiers, he battles against fierce competition, including Emilie’s grandfather, who survives solely to reunite Joey with the memory of his beloved granddaughter.

Ultimately, after moving emotional exchanges, Albert secures Joey and returns home, marking a poignant conclusion to their intertwined fates. Their reunion signifies not just a return to the family farm, but also a testament to enduring bonds, concluding an epic journey of resilience, love, and friendship that flourished even amidst the ravages of war. Albert embraces his parents once more, returning the pennant to his father, symbolizing not just survival, but a legacy of memory and hope.