As the Expendables land in Nepal, their quest to rescue a Chinese businessman from the iron grip of a savage Nepalese militia marks the start of an exhilarating ordeal. Under the courageous leadership of Barney Ross, this exceptional squad consists of the skills of Lee Christmas with his lethal blades, Yin Yang wielding spectacular martial arts, Hale Caesar with his mastery over weaponry, Toll Road who specializes in demolitions, the volatile ferocity of Gunner Jensen, and the sharpshooting excellence of Billy "The Kid". Their mission is straightforward: liberate the businessman and his rival, Trent Mauser. After successfully achieving their goal, Yang heads off to return the rescued businessman to China, while the rest of the Expendables prepare for the challenges that lie ahead.
In New Orleans, Billy expresses his desire to retire and enjoy life with his dear love, Sophia. However, Barney receives an unexpected assignment from Mr. Church, a CIA agent, which sends him and the tech-savvy Maggie Chan on a perilous expedition to Albania to recover a crucial item from a downed aircraft. Their successful retrieval soon turns grim when they encounter the international felon Jean Vilain and his right-hand man Hector, along with the dangerous Sangs gang who have taken Billy captive. Vilain demands the item in a sinister exchange for Billy's life, but despite their compliance, he heartlessly murders Billy, leaving Barney to find a touching farewell note for Sophia. Heartbroken, the team buries their fallen brother, pledging to hunt down Vilain for revenge.
Maggie discloses that the item is a computer containing coordinates to an astonishing five tons of refined weapons-grade plutonium nestled in a derelict Soviet mine. Vilain's plan is to seize this dangerous stash and sell it on the black market. The Expendables track the computer signal to Bulgaria, taking cover at a deserted Russian military base for the night. Their respite is short-lived as they are attacked by the Sangs and a tank, but they are rescued by Booker, an old ally of Barney's, who skillfully eliminates the threats. He shares news of a nearby village where the inhabitants are staunchly opposed to Vilain. Meanwhile, Hector and Vilain commence their plans to unearth the plutonium.
Upon reaching the village, the Expendables are met with an unsettling scene: a group of fiercely armed female villagers defending their children against Vilain's vicious troops. With the menfolk forcibly taken, these brave women plead for the team’s assistance. The Sangs soon attempt to recruit more members, but they encounter a fierce retaliation from the Expendables, who ambush them with precision.
Driven by their mission, the team zeroes in on Vilain's base, pinpointing the mine and executing a daring aerial assault that results in a tactical crash landing. In the ensuing chaos, they rescue the imprisoned miners from their impending doom, yet Vilain and Hector escape with the coveted plutonium. Just as everything seems bleak, Mr. Church and Trench arrive to help free their trapped allies, and they unite to chase down Vilain.
The action escalates at an airport where they confront Vilain and his minions who are preparing a hasty escape. With Booker reintegrated into the battle, the Expendables engage in a fierce showdown alongside Trench and Church against the Sangs. Lee Christmas claims victory by decapitating Hector, while Barney battles Vilain in an intense confrontation. Ultimately, Barney triumphs, delivering a fatal stab to Vilain, putting an end to his reign of terror.
As the climax resolves, Church gifts Barney an old Antonov An-2 biplane before parting ways with Maggie, Booker, and Trench. Meanwhile, in France, Sophia unexpectedly discovers a mysterious package containing a considerable amount of money and Billy's touching letter left at her door. As the Expendables soar into the skies once again, they raise a final toast in honor of their dearly departed comrade, Billy—a heartfelt salute to his enduring spirit.
