In the kingdom of Frell, a baby girl named Ella (Anne Hathaway) is born to Sir Peter and his wife Lady Eleanor. She is given the "gift of obedience" by a misguided and obnoxious fairy called Lucinda (Vivica A. Fox). This turns out to be more of a curse, as it forces Ella to do anything she is told to do, even if the command is against her wishes. Ella's mother, on her deathbed, warns her daughter not to tell anyone about the curse she is under for fear that someone might use it to exploit Ella. After her mother's death, only Mandy (Minnie Driver), the household fairy, knows the secret.
Several years later, Ella's father (Patrick Bergin) remarries to a wealthy socialite, Dame Olga (Joanna Lumley), who dislikes Ella. Her spoiled daughters Hattie (Lucy Punch) and Olive (Jennifer Higham) notice Ella's obedience and start to humiliate her. Ella stumbles upon Prince Charmont (Hugh Dancy), the handsome heir who will soon take the throne, as he's being pursued by his fan club of besotted young women. He invites Ella to the Coronation Ball, but Olga intercepts the invitation. Hattie and Olive, fan club members themselves, are overcome with jealousy. They force Ella to insult and cut ties with her best friend Areida (Parminder Nagra).
Ella cannot bear her situation a moment longer, and resolves to find Lucinda, as she is the only one who can reverse the spell. Mandy helps by lending Ella her boyfriend Benny (Jimi Mistry), who she accidentally transformed into a talking magical book that can show people in their current surroundings. During her journey, Ella encounters an elf named Slannen (Aidan McArdle), who wants to be a lawyer instead of an entertainer as the laws now require. They are both captured by a group of ogres, who want to eat them. Prince Charmont rescues them and accompanies them to a wedding in the land of giants, where Ella hopes to find Lucinda. En route, Ella opens Char's eyes to the cruelty of the laws oppressing elves and giants established by the acting ruler, Char's uncle Sir Edgar (Cary Elwes). Char invites Ella to visit the palace's Hall of Records and find Lucinda faster. But Edgar's talking snake, Heston (voiced by Steve Coogan), is spying on them.
At the palace, Heston tells Edgar about Ella's obedience, which Hattie confirms when Edgar offers her Char's hand in marriage. Knowing that Char intends to marry Ella, Edgar orders her to kill him when he proposes, and keep the plan a secret. Edgar also reveals that he murdered Char's father. To save Char, Ella writes him a letter, saying she is leaving permanently and cannot explain why, which breaks his heart. She then asks Slannen to tie her to a tree and get the giants to help. Lucinda then appears before Ella, who asks her to undo the "gift" of obedience. Lucinda is offended that Ella doesn't like her gift and simply tells Ella to remove it herself. She unties Ella, gives her a fancy dress, and tells her to attend the ball, where Char almost immediately takes her to the Hall of Mirrors and asks her to marry him.
Ella is about to stab him with the dagger Edgar provided, when she realizes Lucinda has provided the answer: looking into a mirror, she says, "You will NO LONGER BE OBEDIENT!" She drops the dagger and Char sees it. But Edgar is spying on them, and before Ella can explain, he orders the guards to lock her up and be executed the following day.
Meanwhile, Benny informs Slannen, the giants, and the ogres that Ella is in trouble, so they all sneak into the castle to rescue her. They find out that Edgar is poisoning the crown Char will receive during the ceremony. Ella and her allies burst in just in time to stop him putting it on. Edgar and Heston call for the knights and Red Guards, and a battle ensues. Ella explains everything while fighting alongside Char, while Mandy manages to transform Benny back into a human. When Edgar's forces lose, Heston tries to bite Char, but is stopped by Ella. Caught trying to kill the prince, Edgar admits to the crowd that he killed the King, but says only he deserves the crown. Then, carried away by his own rhetoric, he puts it dramatically on his own headâpoisoning himself.
Char and Ella kiss; her stepsisters arrive and order her to stop, but she happily refuses. Char once again asks Ella to marry him, and she agrees: "Now that I'll do." The movie ends with their wedding and a musical number. During all this, it's shown that Slannen is in a relationship with a giant (Heidi Klum), Ella has rekindled her friendship with Areida, and Edgar has survived. The Narrator announces two final words: The End.
Who provided Ella the answer ?
Lucinda