Resume : Once upon a time, a single drop of sunlight falls to Earth and becomes a golden flower filled with incredibly strong healing properties. An old witch named Mother Gothel discovers the flower and hoards its healing ability through a song to keep her young for hundreds of years. Centuries later, the pregnant Queen of a nearby kingdom falls deathly sick, leading the King to seek out the legendary mystical plant. Despite Gothel's efforts to hide it, the flower is found, uprooted, and boiled into medicine for the queen, which heals her. The Queen gives birth to a girl, Princess Rapunzel, who has beautiful golden hair that possesses magical healing properties. Gothel, wanting to reclaim her immortality and youth, breaks into the royal nursery to cut a lock of Rapunzel's hair, only to discover that doing so causes it to lose its magic. She kidnaps the Princess instead, raising her as her own in an isolated tower. The King and Queen honor their missing daughter by releasing floating lanterns on the night of her birthday each year in hopes that one day, their Lost Princess will return.

For her eighteenth birthday, Rapunzel asks Gothel for permission to go outside the tower for the first time in her life in order to see the source of the annual floating lights, but Gothel refuses and says that the outside world is filled with dangers. Meanwhile, a thief named Flynn Rider and his partners, the Stabbington brothers, steal the tiara of the lost princess. During the ensuing chase, Maximus, horse of the Captain of the Guards, is separated from his rider but continues on his own. Flynn betrays his accomplices, takes the tiara, and stumbles upon Rapunzel's tower. Rapunzel knocks him unconscious, hides him, and takes the tiara. She asks Gothel for a special paint, the ingredients for which require three days of travel. Gothel leaves and Rapunzel tells Flynn that she will give him the tiara if he takes her to see the lights. While on the route, he takes her to the Snuggly Duckling Inn, which is full of Gaul thugs, in hopes of scaring her into giving up her quest. The thugs are charmed by Rapunzel, who encourages them to follow their dreams.

Fearing that someone might find and identify Rapunzel, Gothel returns early to the tower and finds the tiara. She teams up with the Stabbington brothers so that she can find Rapunzel and the brothers can capture Flynn. The guards invade the tavern and chase Rapunzel and Flynn to a dam which collapses. Flynn and Rapunzel become trapped in a flooding cave. Believing he is about to die, Flynn tells Rapunzel his real name: Eugene Fitzherbert. Rapunzel admits her hair glows when she sings, then realizes they can use the light from her hair to find a way out. Rapunzel later uses her hair to heal Flynn's injured hand. When Flynn goes to gather firewood, Gothel appears and claims that Flynn does not truly care for her. Gothel gives Rapunzel the tiara, suggesting that she test Flynn by giving it to him. The next morning, Maximus confronts Flynn but Rapunzel befriends the horse and convinces him to help them instead. Arriving at the kingdom, Flynn takes Rapunzel around the city, and at night he takes her to see the lanterns. There, Rapunzel gives Flynn the tiara. He realizes he has fallen in love with her, and just before he is about to kiss Rapunzel, he spots his old accomplices and leaves Rapunzel to give them the tiara. The Stabbington brothers knock him out, tie him up on a boat, and send him across the lake. They tell Rapunzel that Flynn betrayed her, and they attempt to kidnap her. Gothel stages a rescue by knocking the brothers unconscious and takes Rapunzel back to the tower. Rapunzel realizes she is the Lost Princess and attempts to flee the tower, but she is captured by Mother Gothel.

Flynn is arrested and sentenced to death, but he is rescued by Maximus and the Gaul thugs from the inn. Flynn races back to the tower and finds Rapunzel chained to the wall and gagged. Gothel fatally stabs him with a knife. Rapunzel agrees to be Gothel's willing prisoner if she is allowed to heal Flynn. However, Flynn uses a shard of glass to cut all of Rapunzel's hair short, causing it to lose its power. Gothel is horrified, and she rapidly ages to death and turns to dust. With his last breath, Flynn declares his love for Rapunzel. Rapunzel, heartbroken, sings the healing song. A single tear, still possessing the magic of the drop of sunlight, falls onto Flynn's face and resurrects him.

Returning to the kingdom, Rapunzel is reunited with the King and Queen. Flynn ends the film by telling the audience that all the thugs made their dreams come true, he readopted his original name, and that he and Rapunzel married and lived happily ever after.