Reese Marshall was an FBI Agent who specialized in finding missing children. She came to Port Charles help find Sonny's missing daughter Kristina Davis who had been kidnapped. Federal Prosecutor, John Durant thought working to find Kristina would be the perfect opportunity for Reese Marshall to gather information on Sonny which he could use to finally prosecute the mobster. Reese's priority however, was to find Kristina. Initially, it appeared as if Sam was the person responsible for the kidnapping but Reese quickly discovered that Sam was being set up. It soon became apparent that the real culprit was Faith Roscoe who hated Sonny because he had ordered the death of her mobster husband. A meeting was arranged to exchange a hefty ransom for Kristina. During the exchange, Faith's men moved in and kidnapped Michael and Morgan, Sonny's two other children, from their mother's home. Faith quickly fled Port Charles with the children. Reese was hot on her trail. She had she found a message hidden by Michael in his room just before the kidnappers took him. The two words "Louis" and "Anna" led Reese to speculate that Faith had taken the children to Louisiana. Things didn't go well there. A phone call by Michael ended with gunfire and the worst was suspected. Reese, Sonny and Jason were more determined than ever to locate the children as quickly as possible. When they discovered the safehouse where the children are being kept, shots are exchanged. Faith was wounded but the children were nowhere to be found. Luckily a phone call revealed that two young children were spotted at a nearby airport which ultimately led to the recovery of Morgan and Kristina, Sonny's two youngest children. Michael, however, remained missing. It was during this time that we learned the reason Reese went to work for the FBI to find missing children. She told Sonny about her own tragic experience of having her young son kidnapped and murdered by his abductors.

Recovering from her gunshot wound, Faith was taken to court to face a judge for kidnapping the children. While Faith was in the courthouse, a sniper kills her. The sniper was later killed and a picture of Michael, presumably dead, was found on him. With the case seemingly closed, Reese was ordered by her superiors to stay in Port Charles and compile evidence that could be used to prosecute Sonny Corinthos. Reese knew that John Durant was behind the order. Reese was reluctant to use what she has learned about Sonny during the kidnapping case because, against her better judgment, she began having feelings for him. That changed though when Sonny made a move against a rival crime family. She begged Sonny not to retaliate against them but to no avail. Sonny, who was still deeply grieving Michael's death, ignored Reese's pleas. During Michael's memorial service, as Sonny sat stoically beside Carly, the massacre he ordered was carried out. Throughout Port Charles, all those connected to the Sandoval family were murdered. Resigned that Sonny would always choose violence over the law, Reese began building a case against Sonny. In the course of the investigation she discovered that Maria Sanchez, a waitress who saw Jason Morgan in the stairwell moments before the shooting in the Metro Court, was being coerced by John Durant to give false testimony. Durant had drugs planted on Maria's son, Diego Sanchez Alcazar, and was threatening to send Diego to jail if Maria didn't name Jason as one of the shooters in Metro Court. Disgusted with Durant's unethical behavior, Reese refused to help him put Sonny behind bars. She went over to Sonny's to hand over the file she had compiled and told him that she was leaving town. Sonny realized after Reese walked out that he didn't want her to leave town because of his feelings for her. In the hopes of catching up with Reese, Sonny rushed to the front gates. As he reached his front gates them, he saw Reese start to open her car door just as the car exploded. Her injuries were minimal. Sonny, concerned for her safety, snuck her out of the hospital and brought her back to his compound. When Ric found Reese, they decided to set up a sting to prove that John Durant was corrupt. Reese wore a wire to a meeting and was able to get John to incriminate himself. Reese had enough evidence to destroy Durant's career and was able to use that to force him to cooperate with her.

During this time Carly learned from Courtney that AJ was alive, giving her great hope that Michael too was alive. Reese eventually was able to track Michael down at the Quartermaine mansion where he'd been hiding with AJ. Michael had been brainwashed to believe that Sonny and Carly no longer wanted him and decided to give him to AJ to be raised. Resentful of Sonny and Carly, Michael wanted nothing to do with them. Things went from bad to worse when AJ was discovered murdered in his hospital room. Carly was the prime suspect and eventually was taken into custody. Michael, who was deeply traumatized from his ordeal combined with seeing his mother arrested, refused to talk to anyone. It seemed the only people he was comfortable with were Reese and Sam. It was during this time that Michael began having disturbing dreams in which he smothered AJ. Reese soon realized that Michael may have in fact murdered AJ because he was terrified that AJ still posed a threat to his siblings, Kristina and Morgan. Fearing his son would be arrested, Sonny decided to confess to the murder. Things looked grim for Sonny until the end of the trial when Ric, the prosecutor, made an eloquent closing summation that in effect vindicated Sonny. Ric had learned the truth about Michael and wanted to protect his nephew and brother.

After the trial, Reese realized that Sonny that bond he had with Carly ran deep and feared that they would eventually reconcile. She decided to leave town to spare herself further heartbreak. She ended up at the Metro Court where she found Ric drinking at the bar. He too was having relationship difficulties. His pregnant wife, Alexis, wanted a divorce. Ric and Reese lent each other a sympathetic ear as they downed shots of alcohol. Drunk, they ended up back in Reese's room where they made love. The next morning they both realized that their night together was a mistake. Reese was in love with Sonny and Ric was in love with his wife. They decided to part as friends and say nothing. They were interrupted when Sonny knocked on Reese's door. While Ric hid, Sonny asked Reese not to leave town because he wanted to explore their relationship further. Reese was thrilled and gladly accepted Sonny's offer. Once Sonny left, Ric joined Reese in the living room and told her that he was happy that things worked out for her and Sonny. As he left Reese's room Emily spotted him. Reese was unaware of it but Ric wasn't. Ric later found Emily and asked her not to say anything. She disapproved of what Ric and Reese had done but reluctantly agreed not to tell anyone.

Things seemed to go well for Reese and Sonny until Courtney's wedding to Jax. When Reese attended the wedding with Sonny, Carly was not happy to see her ex moving on. After the wedding, Carly asked Lorenzo to marry her. Sonny overheard the proposal and quietly left before either Carly or Lorenzo spotted him. Meanwhile, Michael was having a difficult time dealing with Sonny's relationship with Reese. He desperately wanted his parents to reconcile. When Reese asked Sonny over to dinner and invited Michael as well, Sonny declined the offer. He explained that he didn't think Michael was ready. Reese became quite upset. She was convinced that Sonny viewed her more as a mistress than a girlfriend. Reese told Sonny that until he was ready to have a real relationship she didn't want to see him again. As she was driving, Reese had flashbacks to her high school days and a friend named Caroline. She ended up having an accident. Sonny found her and called for an ambulance. Reese's injuries were minor but required a short stay in the hospital. Monica, her attending physician, was surprised to discover when she reviewed the X-rays that Reese had had extensive reconstructive surgery. Reese was vague about the details but confirmed that she had been in a car accident.

While Reese was in the hospital recovering, she was shocked to see her ex-husband, Evan Tucker, walk into her room. She was furious with him. She blamed him for their son's death. It turned out that Evan was involved with the people who had kidnapped their son, Jamie. Evan refused to cooperate with them despite their threats to murder Jamie. When Jamie was murdered, Reese made it her mission to see Evan sent to jail. Evan was bitter and determined to make Reese pay for sending him to jail. Referring to her as Charlotte, Evan demanded that Reese give him one million dollars or he would tell everyone her secret, including Sonny. Reese was tempted to give into his demands but decided to tell Sonny instead, careful to keep the fact that Evan was her ex-husband and any reference to Charlotte a secret. Sonny asked her to arrange an exchange for the money. Reese made the arrangement but gave Sonny false information. When Reese arrived at the meeting place, she found Evan dead and Ric there. Moments later Sonny and Jason arrived. Ric explained that he had killed Evan in self-defense and urged them to leave so that the police would not find them at the scene. While the police dealt with Evan's body, Ric pulled Reese aside and told her that before Evan had died, he had told Ric that Reese was really Charlotte Roberts, Carly's best friend from high school whom everyone believed had been killed in a car accident. Reese told him that she knew Carly as Caroline back then and that Reese had had an accident that left her horribly disfigured and barely alive. After extensive surgeries to reconstruct her face and months of painful therapy, Reese had learned that her mother had told everyone, including Reese's father, that Reese had been killed in the accident. Ric was understanding and assured Reese that he wouldn't tell anyone about her secret past.

Ric and Reese decided to open a law firm. After John Durant had been shot at the courthouse by a corrupt cop, he was taken to General Hospital. When he awoke from surgery, he was paralyzed and blamed Bobbie because she had been in the operating room. Ric and Reese represented Bobbie in the malpractice case, much to Carly's dismay. She was convinced that Reese was trying to take everything that was near and dear to Carly's heart. Carly's erratic behavior and paranoia escalated to the point where she broke in to Reese's penthouse and hit Reese over the head. While Reese was unconscious, Carly stole a lockbox that she was convinced would reveal all of Reese's dirty secrets. She was right. Inside the lockbox were pictures of Carly and Reese when they were friends in high school. When Reese woke up she found a bracelet that she knew belonged to Carly. She went over to Carly's house and demanded that Carly return the lockbox. When Carly questioned her about what was in it, Reese told her it was filled with mementos of her dead son, Jamie. Carly returned the lockbox, having no desire to disturb the precious memories. Unfortunately it didn't end Carly's obsession with proving that Reese was not whom she claimed to be. As Reese was telling Sonny that she was in truth, Charlotte Roberts, Carly headed over to Sonny's mansion, having just figured out the truth herself. Carly wanted to confront Reese but instead of tossing Reese out, Sonny defended her. Carly was shocked; even more so when Reese accused Carly of destroying her family. Reese revealed that the argument that she and Carly had had all those years ago was a result of Reese walking in on her father and Carly in bed together. Reese felt that Carly had shamelessly pursued her father because she secretly coveted everything that Reese had. Carly defended herself, accusing Dan Roberts of seducing an impressionable teenager. Reese's pain was too deep. After Reese's accident, Reese's mother told Dan Roberts and everyone else that Reese had been killed. As a result, Dan Roberts began drinking heavily and getting into trouble with the law. Then one night, he came home and committed suicide by shooting himself.

The revelations led Sonny to end his relationship with Reese. He understood why she kept her past a secret, but he still viewed it as a betrayal. Carly meanwhile lost everything, including her new husband Lorenzo, who was fed up with Carly's obsession for her ex-husband's love life. Carly confronted Reese in Kelly's where things quickly escalated and punches were exchanged. Carly was devastated when Sonny arrived to separate the two women, and instead of attending to Carly, Sonny was concerned over Reese's injuries. Carly suffered a complete breakdown. One night she ended up standing outside Reese's penthouse balcony in the rain. She watched as Sonny and Reese reconcile and then make love. After they left, Carly walked in and completely destroyed Reese's penthouse and then stole Reese's gun. Carly went over to Sonny's house where she confronted him. Reese was on the phone with Sonny as she heard shots fired. She immediately called the police and rushed over to Sonny's only to find Sonny unharmed. Later, after Carly ended up in the house where Reese used to live, Reese came to the realization that she had blamed Carly when she shouldn't have. Reese's father was the adult and he should never have seduced Carly.

Reese and Sonny managed to get their relationship back on track, but when Reese ended up in the hospital after her and Sonny's shoot out with the Ruiz family, Sonny overheard her and Ric talking and learned that they had slept together. He washed his hands of her as a lover, and Reese realized their romance was truly over. Soon after, Reese was involved in the Port Charles train crash, and broke some ribs, one of which punctured her lung. Reese didn't realize how badly she was injured and continued to try to help the others, but just before help arrived, Reese succumbed to her injuries.