Belle first appears in the fairy tale land, when her father, Sir Maurice, asks Rumplestilkstin if he could help protect his people from the ogres. Rumplestilstin agrees, in exchange for Belle. Maurice and Belle's fiancé Gaston refuse, but Belle, wanting to choose her own path, agrees to go with him.
At first, Rumplestiltskin treats Belle as a maid, but after a few months, the two get to know each other, and develope a relationship. Belle eventually becomes happy to help Rumplestiltskin, and becomes very interested in his life.
Rumplestiltskin eventually asks Belle why she accepted the deal. She tells him that there is little opportunity for women in their land to show their bravery. Rumplestiltskin then decides to let Belle go into town for the day, to which Belle asks why he trusts her to come back. Rumplestiltskin admits, that he doesn't and he doesn't expect to ever see Belle again.
While walking in the forest, Queen Regina comes to Belle, and learns that she is running away from Rumplestiltskin, and that he is Belle's lover. Belle states that she could love him but he is cursed, and darkness has taken root in him. Regina informs Belle that true love's kiss can break any curse. She quickly returns to Rumpelstiltskin (much to his surprise), with the intention of kissing him and freeing him from his curse. When Belle notices the kiss is working, she gets excited, and tells Rumplestiltskin that it's working. When he hears this he becomes extremely angry demanding to know where she learnt this. Belle is confused by his reaction and becomes further confused when he begins yelling at Evil Queen about she "turned her against me". He then accuses Belle of "working alone", wanting to be the hero by "killing the beast". Belle responds with desperation claiming that she truly loves him, however he is unable to believe that anyone can love him. Instead he imprisons her in the dungeon. Shortly after he tells her to leave his castle and never return claiming that he doesn't want her anymore and that his powers are more important to him than she. Belle does not believe this. Instead she calls him a coward - being unable to believe that she could love him and being unable to free himself and be happy. Before leaving she also tells him that he will regret his decision forever being left with nothing but an "empty heart and a chipped cup".
Regina then comes to visit Rumplestiltskin, and lies to him, by telling him that Belle killed herself after her father had her exorcised due to her association with Rumplestiltskin. Although Rumplestiltskin refuses to admit it, he is very upset by the news. Unkown to him, Belle was really alive and had been captured by Regina. However, they do not see each other until after the curse takes affect.
When Regina's curse takes affect, Belle's memory is taken away from her, and she is put into a mental hospital in Storybrooke. She does not remember anything about the fairy tale land, or Rumplestiltskin.
The curse turns Rumplestiltskin into a pawnshop owner named Mr. Gold. However, unlike the other fairy tale characters, Mr. Gold's memory of the fairy tale land, had not been affected by the curse. He still believes Belle is dead, and is still upset by it.
In the Season 1 finale, Jefferson (the Mad Hatter) frees Belle from the mental hospital, and tells her to go to Mr. Gold and to tell him that Regina Mills held her captive. Although Belle does not know that she used to be in love with him, but does as Jefferson says. Mr. Gold is shocked to see her, but very happy, and even though Belle doesn't remember him, he promises to protect her. He leads her out into the woods, and (due to Emma Swan successfully breaking the curse), she remembers her life as Belle and tells Rumplestiltskin that she loves him. Belle then watches Gold put true love potion into a well in order to bring magic to Storybrooke.
In Season 2, the two of them are dating. She knows that even though he can be mean and nasty, she knows that he is not a monster, and there is good inside of him.
At the end of Season 3, she marries Mr. Gold at a small ceremony attended by Moe French (Maurice's Stroybrooke identity) and Archie Hopper (Jiminy Cricket's Storybrooke identity).