In the year 1957, Indiana Jones (Harrison Ford), a celebrated hero from World War II, along with his companion George "Mac" McHale, falls into the clutches of a group of Soviet agents led by the cunning Colonel Dr. Irina Spalko (Cate Blanchett). The Soviets execute a covert operation as they invade a classified site known as "Warehouse 51" in Nevada, coercing Jones into locating a crate that contains the remains of an extraterrestrial that had crash-landed a decade prior near Roswell, New Mexico. Upon retrieving the crate filled with magnetic mysteries, Mac—a man swayed by greed—betrays Jones, aligning himself with the Soviets.
Following an intense skirmish with the agents, Indiana narrowly escapes on a rocket sled, plunging into the sands of a desert. He stumbles upon a desolate town, remnants of a nuclear test site, and miraculously survives a nuclear blast by seeking refuge inside a lead-lined refrigerator. After his return, he finds himself under the scrutiny of the FBI, which suspects him of collusion with the Soviets. As a result, he is offered an indefinite leave from Marshall College to prevent his dismissal.
Things take a turn when he encounters Henry "Mutt" Williams (Shia LaBeouf) at a train station. Mutt informs Indiana that their old ally Harold Oxley has been kidnapped after stumbling upon a legendary crystal skull in Peru. Indiana shares the lore surrounding these crystal skulls, stating they have ties to the mystical city of Akator, where returning one would unlock extraordinary powers. Mutt hands Jones a letter from his mother, who, too, is being held captive—inside, they find a riddle penned by Oxley in an ancient Native American tongue.
Their quest leads them to the enigmatic Nazca Lines in Peru, where they uncover that Oxley had succumbed to madness in a psychiatric facility from the skull's overwhelming influence. He was abducted from this asylum by the Soviets. Within Oxley's cell, crucial clues lead them to the resting place of Francisco De Orellana, a Conquistador who went missing centuries ago while on a treasure hunt for Akator, where they eventually discover the hidden skull.
However, their journey takes a perilous turn when they are seized by the Soviets and taken to their base, where they reunite with Oxley and Mutt's mother—revealed to be none other than Indiana's former love, Marion Ravenwood. Adding to the family twist, Mutt is disclosed to be Indiana's son, Henry Jones III. Spalko, fueled by ambition, believes the crystal skull rightfully belongs to an inter-dimensional entity, which she thinks can grant her side a formidable weapon of psychic warfare.
As the adventure unfolds, the group makes a harrowing escape into the Amazon, but they are quickly recaptured after a misstep involving quicksand. With tensions high, an argument between Jones and Marion leads to Marion being gagged. Yet, in a twist of fate, Jones and Mutt overpower their captors, facilitating a daring escape that results in a chaotic jungle chase, culminating in a clash with giant ants leading to the demise of several soldiers.
After navigating treacherous terrain and evading the Soviets amidst breathtaking waterfalls, they reach the abandoned city of Akator. Mac, playing both sides, has been secretly aiding the Soviets. Once inside the central temple, they encounter relics from various ancient cultures, piecing together that the civilizations worshipped the same "archaeologists" that crossed dimensions.
In a climactic moment, the group discovers a chamber housing thirteen alien skeletons arranged in a circle, but one skull is missing. Spalko steps in at the crucial moment, replacing the skull and triggering a transformative event. The aliens communicate through Oxley, promising a "big gift" to the seekers. However, Spalko's greed leads her to demand an overwhelming knowledge transfer, which spirals out of control, consuming her existence as she ultimately disintegrates.
As the temple crumbles, a magnificent flying saucer emerges, defying logic before vanishing into the vastness of space. Sometime later, peace returns as Indiana is reinstated at Marshall College as an associate dean. He and Marion celebrate their love with a heartfelt wedding, sealing their adventure with a promise of a new beginning.
