In 1912, a Boy Scout troop rides horseback through Moab, Utah. Although their leader warns them not to wander off after they dismount, two boys split from the group and observe a band of thieves stealing artifacts from a nearby cave. Young Indiana “Indy” Jones identifies the thieves’ prized discovery as the Cross of Coronado and tells his fellow Scout to run back and call the sheriff because the cross belongs in a museum. As the thieves return to their work, Indy steals the artifact and a chase ensues, with Indy on horseback and the looters pursuing him in Model T Fords. Indy jumps from his horse onto a passing circus train, enters a reptile car, and falls into a crate of snakes. Terrified, he climbs on top of another train car, snakes still clinging to his clothes, and wrestles one of the thieves at knifepoint. The rhinoceros inside the train car thrusts his horn through the roof and narrowly misses Indy’s private parts. After using a water turret to evade another attack, Indy lands face-to-face with Fedora, the leader of the thieves, and falls through the top hatch of another train car. Inside, Indy is confronted by a lion, but finds a whip for defense and wounds his chin. With no other way out, Indy tosses the whip up to the looters who pull him from the car just as the lion lunges forward. When one of the thieves attempts to snatch the cross from Indy, a snake slithers from Indy’s shirtsleeve and distracts the attacker, allowing Indy to escape yet again using a disappearing act box in “Doctor Fantasy’s Magic Caboose” as his escape route. He runs home, but his father, Henry Jones, is focused on reproducing the drawing of a knight from an illuminated manuscript in his diary and ignores Indy. Indy’s Scout friend arrives with the sheriff, but when Indy hands over the cross, the sheriff tells him that it will be returned to its rightful owner and the band of thieves enters the house. Looking through the window in disbelief, Indy sees antiquities collector, Panama Hat, reclaim his stolen treasure. Impressed by Indy’s perseverance, Fedora tells Indy that even though he lost that day, he doesn’t have to like it, and gives Indy his trademark hat. Twenty-six years later, in 1938 on a storm-struck ship on the Portuguese Coast, Indy is again confronted by Panama Hat and his minions after regaining possession of the Cross of Coronado. As Panama Hat seizes the Cross, Indy repeats his contention that it should be in a museum, fights the sailors and recovers the precious artifact. With waves breaking over the ship’s deck, Indy jumps overboard just as the boat explodes. Clinging to a life ring, Indy sees a panama hat tossed in the waves. Returning to his professorship of archeology at Barnett College, Indy gives the Cross of Coronado to the curator of the National Museum, Marcus Brody. Escaping from an aggressive crowd of student admirers, Indy seeks shelter in his office, finds a package sent from Venice, Italy, and puts it in his pocket. After leaving through the window, Indy is approached by men who escort him to the home of wealthy industrialist and antiquities collector, Walter Donovan. When Donovan asks Indy to translate a 12th century sandstone tablet inscribed with ancient text, Indy realizes the tablet provides directions to the Holy Grail. Donovan eagerly points out that the chalice bestows eternal life, but Indy refers to the story as a legend. Donovan reminds Indy of Henry’s passion for the subject and tells him that although the tablet is not intact, he has started a project to recover the Grail. Donovan reports that, according to ancient lore, the Grail was lost for a thousand years when recovered by three knights of the First Crusade. When Indy adds that a surviving knight imparted his story to a Franciscan friar, who transcribed it into an illuminated manuscript, Donovan shows Indy that the manuscript is in his possession. Although the book does not give the location of the Grail, it notes the existence of two markers, and Donovan claims the tablet is one of them. Donovan tells Indy the other marker, purportedly entombed with a second knight in Venice, Italy, is the site of his recovery project, but the project’s leader has mysteriously disappeared and he wants Indy to find him. Indy tells Donovan that he should ask his father, instead, but Donovan says he already has and reveals that the project leader is Henry. Indy rushes to Henry's house with Marcus and finds it ransacked, but when Marcus observes that the mail has been opened, Indy remembers the package from Venice in his pocket and finds Henry’s Grail diary inside. Concerned for his father's wellbeing, Indy accepts Donovan's request and flies to Venice with Marcus, reading the diary on his way. Upon arrival, Indy and Marcus are met by Henry’s glamorous, blonde colleague, Dr. Elsa Schneider. As she leads them to the library where Henry was last seen, Elsa gives Indy a scrap of paper inscribed with Roman numerals that remained at Henry’s desk after he disappeared. Exploring the grounds of the library, a converted church, Indy notices a stained glass window that Henry reproduced in his diary and Marcus points out its Roman numerals correspond to the note from Henry’s desk. Indy concludes that Henry was not at the library for research, but because it is the site of the knight’s tomb. After breaking through the floor and into a tunnel of ancient catacombs, Indy gives Marcus the Grail diary for safekeeping and he and Elsa descend into the tomb. Meanwhile, shadowy figures knock Marcus out and follow Indy and Elsa into the catacombs. After a harrowing passage through skeletons and rats, Indy finds the second marker in the knight’s tomb and realizes it is his shield. As Indy completes Henry’s rubbing of Donovan’s tablet with the text on the shield, the mysterious figures set fire to the tomb, but Indy and Elsa escape the through a manhole and a boat chase ensues through the port of Venice. After Indy threatens Kazim, one of the assailants, with a spinning boat propeller, Kazim tells him about the Brotherhood of the Cruciform Sword, a secret society sworn to protect the secret of the Holy Grail. When Indy assures Kazim that he has not come for the Grail, but to find his father, Kazim informs Indy that Henry is being held at Brunwald Castle on the Austrian-German border. Returning to the hotel, Indy shows Marcus the paired rubbings of the knight’s shield and Donovan’s tablet. Marcus identifies Alexandretta as the site of the Grail and Indy comments that the city was destroyed by the knights of the First Crusade but rebuilt with the name Iskenderun. Indy instructs Marcus to head for Alexandretta then discovers that his and Elsa’s hotel rooms have been searched. When Elsa wonders what they were looking for, Indy reveals that he has Henry’s Grail diary. Although she becomes enraged that he did not inform her earlier, they kiss passionately and make love. Later, they journey to Brunwald Castle only to realize it is a Nazi stronghold. After using his whip to swing between the castle’s towers and crashing through a window, Indy lands in Henry’s chamber. Henry is overjoyed to learn that Indy used his diary to discover the tomb and Alexandretta as the site of the Grail, but German officers enter the room and hold Indy and Henry at gunpoint, demanding possession the diary. When Henry berates Indy for bringing the diary with him, Indy seizes a machine gun from an officer and shoots the Germans. As they flee, they are confronted by another officer who holds a gun to Elsa’s head. Although Henry warns Indy that Elsa is a Nazi, Indy puts down his weapon. Falling into Indy’s arms, Elsa apologizes with feigned sincerity and takes the diary. When Indy asks how Henry knew she was a Nazi, Henry suggestively professes that she talks in her sleep. Donovan then appears and presents himself as a Nazi collaborator, but soon discovers that the pages in the diary containing the map are missing. Elsa contends that they are with Marcus, but Indy claims that they will never find Marcus because he will blend into Egyptian society due to his vast knowledge of the region and its language. Meanwhile, Marcus stumbles into Iskenderun disoriented and unable to communicate, but is reunited with his former associate on archeological digs, Sallah. Two men claiming to be from the Museum of Antiquities approach Marcus and Sallah in the bazaar, and although Sallah tells Marcus to run, Marcus is captured by the Nazis. Back at Brunwald Castle, Elsa leaves for Berlin with Henry’s diary as Indy and Henry are confined. In their attempt to break free, Henry drops Indy’s lighter and starts a fire. Meanwhile, Donovan receives news that the map has been obtained from Marcus and that the Führer has ordered Henry and Indy dead, but the men escape through a hidden stairway and outrun the Nazis on motorcycle. At a crossroads, Henry explains that his diary contains vital clues to overcoming the three challenges that will face the person who finds the Grail, and they follow Elsa to Berlin. Indy is aggravated by the detour from Iskenderun, but Henry tells him that the quest for the Grail is not archeology, but rather a fight against evil. In Berlin, Indy confronts Elsa at a Nazi rally disguised as an officer. When he recovers the diary, Elsa argues that she only cares about the Grail, not the Nazis. Indy is then pushed into the crowd and finds himself face-to-face with Hitler, who mistakes the diary for an autograph book and signs his name. The next day, Indy and Henry board a Zeppelin to escape Germany, and, after pushing a Nazi officer off the flight, Indy tells Henry that he wished for more emotional attention when he was a boy. Henry diverts their attention to the three challenges of the Grail described in his diary: the Breath of God, the Word of God and the Path of God. The airship then begins to turn around mid-flight and Indy and Henry are forced to escape in an airplane. After fighting a gun battle with German planes, Indy crash-lands and the men steal a car, dodging bullets and bombs. Meanwhile, in the Republic of Hatay, Donovan negotiates with the king for support of the Grail expedition while Kazim, disguised as an attendant, looks on. After arriving in Iskenderun, Indy and Henry are met by Sallah, who explains that the Nazis have abducted Marcus while driving them to the desert. As they watch Donovan’s convoy from afar, the Brotherhood of the Cruciform Sword fires on the Nazi caravan, but are swiftly defeated. With his dying words, Kazim warns Donovan and Elsa that the Grail possesses eternal damnation while Indy and Sallah steal horses and camels from the Nazis. Meanwhile, Henry finds Marcus in a tank, but they remain trapped inside. Indy chases them on horseback, jumps onto the tank, and fights the officers while Henry and Marcus gain control of the vehicle from within. As the tank heads toward a cliff, Marcus falls off and Henry is rescued by Sallah on horseback, but Indy is missing when the tank crashes and explodes, and Henry laments the death of his son. When Indy returns, Henry is finally able to show Indy his emotions. At the same time, Donovan and the Nazis locate the Canyon of the Crescent Moon and enter its temple. When Indy, Henry, Marcus and Sallah arrive at the scene, they witness a young soldier sacrifice his head as he attempts to approach the Grail. Donovan forces Indy to enter the cavern of the Grail by shooting Henry in the stomach, claiming that only the healing power of the Grail can save his father. As Indy makes his way toward the Grail, Indy and Henry mutter instructions from Henry’s diary. For the first challenge, the Breath of God, Indy kneels in penitence just as giant, round blades swipe at his body. Reading from Henry’s diary about the second challenge, the Word of God, Indy notices letters engraved in the stone path. As both Indy and Henry realize the word is “Jehovah,” Indy forgets to use the Latin spelling, which starts with an “I,” and stumbles through the stone engraved with the letter “J.” After safely passing through the remaining letters, Indy faces the third challenge, the Path of God, and reads from the diary that only a leap from the lion’s head will help him across the massive fissure. As Henry cries in pain and Marcus anxiously tells Indy to hurry, Indy realizes that the crossing is a leap of faith. A bridge magically appears under his feet after he takes the first step. When Indy enters the final chamber he is attacked by the Grail Knight but the man is weak and can barely hold his sword. The Grail Knight tells Indy that he is the last of the three knights who swore to protect the Grail 700 years earlier. Assuming Indy is a fellow knight who has come to vanquish him, he hands over his sword when Donovan and Elsa appear in the chamber. Donovan asks which of the many vessels is the Grail, but the Knight only reveals that Donovan must chose wisely because the false Grail will take his life. Elsa surreptitiously offers to select the Grail for Donovan, but when he drinks from it, he ages within seconds and decays into a pile of dust. Elsa then tells Indy that the Grail would not be made from gold and he selects the least conspicuous cup and drinks from it. The Grail Knight assures Indy that he has chosen wisely, but warns him not to take the Grail past the Great Seal. Indy returns to Henry with the Grail and its water instantly heals his father’s wound. Elsa becomes overwhelmed by the chance to possess the Grail and steps across the Great Seal holding it, causing the earth to crack beneath her. Indy grabs her arm as she slips into a fissure, but she insists on reaching for the fallen Grail and drops to her death. When Indy tumbles after her, Henry holds his arm. Indy, however, is also tempted by his close proximity to the Grail. As Indy struggles to reach the Grail, Henry tells him to let it go and Indy grabs his father’s hand and is pulled to safety. The Grail Knight waves farewell as the two men run outside and the cavern collapses. When Henry explains that Elsa confused the Grail for a prize, Indy asks Henry what he discovered and Henry replies: Illumination. Joining Sallah and Marcus on horseback, the four friends ride into the sunset.