Sierra Estaban, the daughter of former Montega ruler Jacobo Estaban, had her life thrown into turmoil by a revolution. Revolutionaries had captured and murdered her father and were going after her. Luckily, Sierra, who avoided capture by disguising herself as a boy named Carlos, was able to escape from Montega with the help of a stranger, Craig Montgomery. To keep her safe, Craig brought Sierra to Oakdale and got her settled in the home of her godmother, and his boss, Lucinda Walsh. The loss of everything she had led Sierra to begin a search for the mother she never knew. Sierra had been told that her mother, Mary Ellen Walters, had died in Montega and was shocked to learn that that was a lie. Though her search led to a dead end, she later found out that her mother was none other than Lucinda Walsh herself! Feeling betrayed that both Lucinda and Craig kept the truth from her for months, Sierra ran away and impulsively married her countryman, Tonio Reyes.

The marriage proved to be a disaster. Not only was Tonio a chauvinistic womanizer, but Sierra found that she couldn't stop thinking about Craig. Sierra's preoccupation didn't go unnoticed by Tonio and he threatened to kill Craig if he went near Sierra. Scared for his life, Sierra shared one night of passion with Craig before ending their relationship. Soon, Sierra found herself pregnant. Finally fed up with Tonio's affairs, Sierra divorced him and gave birth to a boy, Bryant. Soon after his birth, Sierra was thrilled to learn that Craig was the boy's father and the two married.

Sierra's life went into turmoil again when she returned to Montega to rebuild her father's home. While in Montega, Sierra was kidnapped by revolutionaries and held hostage. Luckily, Sierra was able to escape and she started fighting for the Montegan resistance. After a few years, her troops were able to squash the rebellion and she was reunited with her family. Soon after, she resettled with her family to Miami and had another child, Lucinda (Lucy) Marie. Unfortunately over the years, Sierra and Craig's marriage crumbled due to lack of communication and conflicting goals. Though the two tried to patch together their marriage, in the end, Craig left Sierra and the two divorced.

Years later, Sierra would send a troublesome Bryant to Lucinda's in the hopes that the boy would find direction in his life. At about the same time, a wayward Craig made it back to Oakdale as well. Though Craig and Sierra still had strong feelings for each other, they recognized that they were incompatible and remained friends. Following Bryant's tragic death, a reluctant Sierra let Lucy stay with her father but visited often to provide guidance and became a supporter of Lucy's relationship with Aaron Snyder.

A few years later, in 2004, Sierra would come to Oakdale again with a surprise--a new husband, Alan Drake. As this new and exciting life was opening up for Sierra, Craig's life was falling apart since he'd lost his wife and newborn baby because he had adopted the baby illegally. Having lost everything, including Lucy's respect, Craig was on a downward spiral that included drinking and embarrassing Lucy on her graduation day from high school. Concerned about Lucy, Sierra suggested that she come to Montega for the summer. She and Alan then left. However, the day Lucy was set to leave, she was suddenly kidnapped! Needing to know what was going on, but unable to leave Montega, Sierra sent Alan to Oakdale on her behalf. Weeks later, Lucy was found. Although it was originally thought that Dusty Donovan had kidnapped Lucy, in reality he was protecting her from the real kidnappers, who Dusty believed were hired by a member of Lucy's family. Although Craig would reluctantly voice his theory that Alan arranged the kidnapping to get ransom money, Sierra refused to believe it. Later, when Lucy was kidnapped again, Alan ended up getting shot trying to pay the ransom money. At the hospital, he whispered Craig's name before dying. With that, things suddenly clicked in Sierra's mind and she realized that Craig set up Lucy's kidnapping! After meeting with Dusty, and learning that he shared her theory, that Craig arranged the kidnapping so he could play the hero, Sierra decided to clear Alan's name and nail Craig. Although they succeeded in getting evidence against Craig, Dusty gave the evidence to Lucy, who refused to turn in her father.

However, even though Lucy had refused to press charges against Craig, that didn't mean that she had forgiven him. As Lucy tried to distance herself, Craig continued to try to insinuate himself into her life. Deciding that she had to protect Lucy from Craig's interference, Sierra moved back to Oakdale. She then decided to get revenge on Craig and force him to face the consequences of his actions by having him kidnapped. Planning on keeping Craig locked up in a monastery until he repented, Sierra kept a close eye on him, via surveillance camera. The plan appeared to be working, with Craig praying for guidance and seeming truly sorry for what he'd done. Although she wasn't sure if he was being sincere or not, it became a moot point when he was rescued by his sister, Margo.

Later, after supporting Lucinda through her cancer scare, Sierra left Oakdale again for Montega. Years later, a young man named Gabriel Carras arrived in Oakdale, unsettling Lily. Gabriel was the product of an affair Craig had with a maid while he was married to Sierra. The boy's mother, Lydia, asked that Craig not be told, and Sierra kept the secret telling no one but Lucinda and Lily. Now, almost twenty years later, Lily was convinced that Craig deserved to know the truth and, against Lucinda's advice, told Craig who Gabriel was. Soon after, Lucinda summoned Lucy to Oakdale and Sierra warned her mother not to use Lucy as a pawn against Craig. When it appeared that Lucinda was using her to distract Craig, Lucy left town. Later, Gabriel accepted Sierra's job offer in Montega.