Broken Vow is a story about Melissa Santiago, a street-smart woman played by Bianca King whom Roberto Sebastian (Gabby Eigenmann), a rich councilor, fell madly in love with.

Despite their difference in social status, Roberto wants to marry Melissa.

But an unfortunate event happened to Melissa. She was abducted and raped. 

Roberto stands by the woman he loves. On the eve of their wedding, Melissa finds out that she is pregnant.

After learning the truth, Roberto changes his mind and dumps Melissa on the day of their wedding.

Melissa feels devastated and plans to end her life by jumping off a bridge. Felix Rastro (Luis Alandy) recues her and the two eventually end up getting married.

Roberto then marries ex-girlfriend Rebecca Sta. Maria (Rochelle Pangilinan).

But Roberto then realizes that he still loves Melissa and wants to win her back.