Was at one time a con artist
Infected the townspeople with a toxin, resulting in several deaths 
Held the vaccine/antidote for the toxin for ransom 
Imprisoned in the Maarkam Islands for stealing jewels [May 2006]
Arrested for stealing jewelry from Tracy Quartermaine, charges were dropped [May 2009]
Helped Luke Spencer hack into files at a bank in Switzerland [Aug 2013]
Holly was introduced when Luke met her during a camping trip. He saw her swimming and was immediately smitten. They ended up having a one-night stand. Unbeknownst to Luke, Holly orchestrated the meeting. Holly was a key player in an oil scam meant to swindle the citizens of Port Charles. Luke refused to believe that Holly was a professional grifter and went to great lengths to prove she was innocent but eventually Holly was forced to admit the truth. When Holly helped Luke to bring down her family, Holly was kidnapped. Luke and Robert Scorpio traveled to Vancouver Columbia to rescue Holly and recover the money stolen by her ex-cohorts. Still hurt over Holly's deception and unable to fully trust her, Luke and Holly ended up having a terrible argument. In a fit of anger, Luke packed his things and headed to the mountains. Shortly afterwards, news arrived that there had been an avalanche. Since Luke had disappeared everyone believed he'd been killed. The truth was, Luke had broken his back and was recuperating in a remote hospital. To make matters worse, Holly discovered that she was pregnant with Luke's child and about to be deported. To honor his friend, Robert offered to marry Holly and help raise Luke's child. Sadly, shortly after the wedding Holly suffered a miscarriage.
Both Robert and Holly received a shock when Luke returned to town very much alive. Luke was deeply hurt to find out his best friend and his ex-lover not only married but had fallen in love. Later that year though, after Luke was elected mayor, Laura returned to Port Charles and Luke's loving arms.
In 1985, Anna Devane came to town and struck up a friendship with Holly. Holly was shocked to learn that her friend shared a past with Robert. After discovering Robert and Anna were former WSB partners, Holly demanded the truth. Holly thought the only thing Robert was concealing was his guilt over Anna's scar. She was not prepared when he revealed that Anna was his wife! Holly was outraged! She stormed out of their penthouse and headed for London, determined to stay away from Robert. Eventually they reconciled and decided to move to Australia but before they could leave Robert found a young girl in his home. It would later be revealed that the young girl was his daughter, Robin whom Anna kept secret. When Robin overheard Anna and Robert talking, she realized that they were her parents. Hurt, she ran away and ended up in General Hospital where she was later kidnapped after she found some precious black pearls. Robert and Anna eventually found her and Robert left for Australia to be with Holly.
He returned in 1987 with the sad news that Holly had been killed in a plane crash. In 1992 after Robert and Anna married, Holly returned to Port Charles. It turns out that she had been in a car accident and had been in a coma. Realizing that Robert was in love with Anna, Holly decided to stay away from Robert.
Before going in search after his kidnapped "wife" Anna, Robert had divorce papers drawn up to dissolve his marriage to Holly. However, after his and Anna's death, Holly tore up the divorce papers, helped Mac care for Robin for a while and dated Bill Eckert, Luke's look-alike cousin, before leaving Port Charles in 1993.
Holly resurfaced in 2006 when many residents of Port Charles were infected with a deadly encephalitis virus that Luke Spencer had inadvertently picked up in the Maarkam Islands. Holly possessed the antidote to the virus and she anonymously contacted Robert and offered to turn it over for one million dollars. Luke Spencer provided the money and joined Robert in an attempt to trade for the cure. Holly made a move for the money but disappeared without it when she realized there was an ambush waiting for her. She remained in possession of the antidote and set up another meeting with Robert.
In the original attempt to obtain the money, Holly had dropped a candy bar wrapper. Luke sensed something familiar about the wrapper and he and Robert theorized that the mystery woman had once lived in Port Charles. Luke's niece Carly Corinthos also recognized the wrapper because it was exclusively sold at her hotel, the Metro Court. Carly broke into Holly's room and tried to get the briefcase which held the antidote but Holly knocked her out and disappeared.
Holly and her associates tried to leave town with the antidote but Jason Morgan and Carly were able to get their hands on the cure and delivered it to the hospital. Meanwhile, Holly was about to escape when she was tracked down by Luke and Robert. She fired a shot at Luke and threatened to poison the water if Robert did not let her go. When he refused to back down, she confessed to Robert that she still loved him and would like to run away with him. He pretended to accept her offer but instead moved in closer to disarm her. Holly was extradited back to the Maarkam Islands to pay for her crimes.
A few months later, on the eve of Luke's renewal of wedding vows to Tracy Quartermaine, Holly contacted Luke and asked for his help. She claimed she was no longer safe in prison because the guards planned to kill her. Luke arrived and rescued Holly and she thanked him by evading him. Holly left Luke tied up to a bed while she lounged in another room. Robert found them both and the three argued about the events that had transpired. Robert was arrested and Holly and Luke formed a plan to break him out of jail, although it did not work and all three of them were imprisoned.
Luke, Robert, and Holly all escaped from prison and they took off into the jungle. The men fought for Holly's affections but she turned them both down and led them to safety at her late husband's villa. They planned to hide until the police called off their search. Holly was surprised when they received company at the villa. Robin and her colleague Patrick Drake arrived to check on Robert, and Luke's daughter Lulu showed up with her crush Dillon Quartermaine. Holly flirted with Patrick and he encouraged the behaviors, much to the annoyance of Luke, Robert, and Robin.
Bounty hunters arrived and confiscated the stolen jewels that were in Holly's possession. Robert and Luke managed to get the jewels back and send the bounty hunters away temporarily. The confusion over who had the jewels continued as Anna arrived, and soon after, Luke's wife Tracy Quartermaine. Everyone made plans to leave the Maarkham Islands before the bounty hunters returned again and the guests of the villa started to depart. Holly boarded a plane and escaped with the jewels until Anna showed up and took them from her.
In 2009, Holly contacted Luke again and led him to Singapore, although he did not arrive alone. A young man named Ethan Lovett and Tracy joined him. Holly did not reveal herself but instead watched the group as they engaged in a bar fight with the locals and returned to Port Charles. Holly followed them and met up with Luke at his casino, the Haunted Star. Luke and Tracy suspected that Ethan was Holly's son with Luke and Luke wanted to know if the theory was true. Holly offered to share the information for a price.
Holly visited Patrick at the home he shared with Robin but their visit was interrupted by Luke and Ethan. They demanded to know the truth about the identity of Ethan's parents. Holly remained elusive with her comments although Luke theorized Holly was Ethan's mother after Ethan explained that when he and Holly had first met in a poker game, she had not tried to seduce him. Holly reminded Luke she would answer all his questions after he paid her with Tracy's money and offered to run away with him.
Ethan, Tracy, and Luke realized Holly's true intention for coming to town was to seduce Luke away from Tracy, not to clear up Ethan's identity. Tracy offered Holly two million dollars to leave town without Luke, but she refused and said she was not going without him. Holly changed her mind about withholding the truth for money after Luke's son Lucky spoke to her about how Luke's entire family was affected. Holly found Ethan and Luke and stated that she was Ethan's mother and that Robert was his father.
Tracy was determined to keep Holly away from Luke and she framed Holly for stealing her jewelry and she was arrested. Tracy offered to drop the charges against her if Holly agreed to leave town without Luke. Holly agreed to the deal and she visited Luke and Ethan one last time and admitted that Luke was Ethan's father. Ethan was angry that Holly had lied to him and stormed off but Luke wanted to know why Holly had kept Ethan a secret. She confessed that years ago by the time she had learned she was pregnant with Luke's child he had already reconciled with Laura and was happy. She chose to give Ethan up for adoption but lead him to find Luke after his adoptive parents had been killed.
Ethan returned and thanked Holly for allowing him to grow up in a loving home and was disappointed when Holly admitted that she was on her way out of town. Holly and Luke said good-bye as Tracy interrupted, and Holly threatened that she would be back for Luke if Tracy ever treated him poorly.
Holly did return to Port Charles a few years later and she arrived at Wyndemere as Helena Cassadine held Luke and Ethan in her clutches and planned to shoot Ethan. Helena had intended to punish Luke for killing her son Stavros by forcing Luke to watch her kill his son. Holly intervened and rescued them both from Helena and foiled Helena's revenge when she announced Robert Scorpio was Ethan's father. Helena disappeared after she took a hair sample from both men to run her own DNA test.
After Helena left, Ethan and Luke wondered if Holly's paternity claim was true until she admitted she had lied to protect Ethan. Around the same time, Robert's daughter Robin was presumed dead and Robert struggled to find a reason to go on. Luke renewed Robert's spirit by repeating Holly's lie that Robert was actually Ethan's father and that Ethan was in danger from Helena. Holly was displeased with the plan but she agreed to go along with Luke's decision when Robert came to her looking for Ethan. After Robert took off in search of Ethan, Holly hoped she had made the right choice.
Holly resurfaced in Switzerland months later after Robert had been injected with a neurotoxin by Cesar Faison's associate Dr. Liesl Obrecht. As Robert remained unresponsive in a Swiss clinic Holly remained by his side. She took a break from her vigil when Luke needed assistance breaking into a Swiss bank to view financial records related to Jerry Jacks. Luke, like Jerry, had been poisoned with the radioactive substance Polonium and Luke believed that Jerry had found a cure. Both Luke and Holly were shocked when they realized that Sean Donely had partnered with Jerry. Sean explained that he had also been poisoned and agreed to work with Jerry in exchange for the cure. However, Jerry had not fulfilled his end of the partnership and Sean offered his assistance to Holly and Luke in their search for the cure.
The search for Jerry led Holly and Luke to Corinth, Pennsylvania. Jerry was gone by the time they arrived but they did find Dr. Obrecht. While Luke was occupied elsewhere, Dr. Obrecht admitted to Holly that she had created a cure for Polonium poisoning and offered to use her medical expertise to revive Robert if Holly let her go. When Luke returned, Dr. Obrecht was gone and Holly was unconscious on the floor. After Holly regained consciousness, she claimed that Dr. Obrecht had overpowered her. Then Holly took off in search of Dr. Obrecht and the Polonium cure.