Sebastian Hulce's arrival in Springfield was shrouded in intrigue. Expecting a visit from her father, former town villain Roger Thorpe, Blake Marler was surprised to meet Sebastian instead. Sebastian claimed to be an associate of Roger's and later delivered some startling news to Blake and her mother, Holly Reade: Roger had died from a lengthy illness. Although a shocked and saddened Blake immediately believed Sebastian, Holly was more skeptical. However, Sebastian was able to offer proof--Roger's ashes. He then revealed another secret--he was Roger's long lost son. Sebastian told the pair that he had come to town to finish what Roger started and needed their help. That same day, Sebastian placed a call to Michelle Bauer Santos, inquiring about the lighthouse that she was planning on turning into a restaurant. With an agenda of his own, Sebastian approached Michelle about buying the lighthouse but she refused to sell. Not long after, Sebastian confronted Holly with the knowledge that he knew she'd run a DNA scan on him by using a lock of hair she'd gotten from his jacket. While Sebastian's intensity began to terrify, yet intrigue, Holly, Blake was quickly bonding with her newfound brother, especially after he saved her from some muggers. He then revealed that he knew what the muggers were after--a gold coin that Roger had given to her. Later, upon learning that Michelle had been a victim of various muggings as well, Sebastian informed her that it was for the same reason, and offered to take the coin off her hands. However, unbeknownst to both women, the muggings were set up by Sebastian himself.

Not long after, Sebastian suggested to Blake and Holly that they go on a journey to collect Roger's legacy and celebrate his life. Although Holly declined, Blake immediately accepted the offer. However, Holly couldn't get Sebastian's offer out of her head, and had a change of heart and agreed to go along. Also invited along was Michelle Bauer. Although Blake was an unexpected no-show, Sebastian departed with Holly and Michelle, and stow away Tony Santos who didn't trust Sebastian. Though Holly tried to back out when she learned that Sebastian was taking them to Santo Domingo--the place where Roger had kidnapped her decades earlier--Sebastian was able to convince her that the trip would help her settle her demons. On the way to the island, Sebastian discovered Tony and pulled a gun on him, frightening Holly. Wanting to diffuse the situation and gain Holly's trust, Sebastian covered and welcomed Tony. Soon they arrived at their destinati0n where Holly was unnerved when she was taken to the same hotel were Roger kidnapped her years earlier. When she spotted a waiter who resembled Roger, she became unglued, but was quickly calmed down by Sebastian. He persuaded her not to be afraid of her past and read her a message from Roger that affected her. Later, Sebastian took her through a series of caves to Roger's last retreat, a bunker-like Spanish villa on a deserted island. Although she was fearful and wondered if Roger was perhaps still alive, she was eventually able to get over the horrors of her past and find closure. Just as Holly was ready to retrieve Roger's treasure and leave, she discovered that Sebastian had his own agenda--he was dying and would not release her until Ed Bauer arrived to cure him. With that announcement, he locked a horrified Holly in a cell down in the cave.

Over the next several days, Holly begged Sebastian to let her go, but he refused. In defiance, Holly staged a hunger strike which dismayed Sebastian. When he doubled over in pain during an argument, Holly tried to get him to go the hospital, but he refused. When Holly saw how vulnerable he was, she pretended to soften towards him. That same day, she tried to bribe one of his servants to let her go, but unfortunately, the servant refused and told Sebastian of the attempt. Angry, Sebastian raised a hand as if to hit Holly, but refrained. Days later, in an effort to escape, Holly tried to seduce Sebastian in the hopes he'd let her go, but he realized what she was doing. During the course of this failed seduction, as Holly was kissing Sebastian, he was suddenly hit with a severe pain and pulled back. After becoming angry that Michelle had not yet brought Ed to help him, he stormed out and left. He then returned to Springfield to get some answers. Believing Danny knew where Michelle was, Sebastian confronted him, but Danny was evasive. A little later, at Cedars to get medication, Sebastian came face to face with Blake, who was asking questions about where Holly was and why she hadn't heard from her mother; Sebastian insisted that she was fine and just wanted to be alone. Although she tried to insist on speaking with Holly, Sebastian convinced her that there was nothing to worry about.

Later, Sebastian finally fiound Michelle--right there in his villa! Sebastian then had both women locked in the cage together. He then demanded that she get in touch with Ed, but she refused unless he rescued Tony who had been bitten by a poisonous spider and was lying delirious in the jungle. Sebastian complied, only to have Michelle double-cross him by calling Danny instead of Ed. Furious, Sebastian imprisoned all of them and threatened to kill them. Finally, Michelle persuaded Sebastian to let her create the formula. However, by this point, Sebastian was becoming increasingly more paranoid and violent and he refused. Though Holly convinced him to let Michelle try, it turned out to be a trap with Michelle concocting a drug to knock Sebastian out. Luckily for him, Holly warned him before he took it. Betrayed, Sebastian was ready to kill all of them, when Tony volunteered to find Ed himself. Though he was against it at first, Holly convinced Sebastian to let Tony try. On the outside, Tony ran into Michelle's husband, Danny (who had become suspicious because of Michelle's phone call) and Danny went to Sebastian's villa to rescue Michelle and Holly. When Danny headed off in his plane to rescue Michelle, Sebastian's men tampered with the plane and Danny found himself in grave danger. Meanwhile, Sebastian informed Michelle and Holly of the crash and told both that Danny was dead. It wouldn't take long for the women to learn that Sebastian had lied when Danny suddenly showed up at the villa. Unfortunately, Danny's injuries left him week and ended up being another hostage.

Finally in 2005, Tony found Ed's notes in Africa and Michelle was able to synthesize a cure. When an increasingly paranoid Sebastian was unwilling to try the antidote, thinking it was a trick, he ordered Danny to do it. Danny agreed, only if he released Holly and Michelle. When Sebastian balked at that, Michelle tried the antidote herself. Finally cured, Sebastian released the hostages but Holly stayed behind to say a final goodbye. Unfortunately, he wasn't finished with her yet. Alone with her on the helicopter, Sebastian made a convincing argument for why they should be together but Holly ultimately resisted temptation and insisted on returning home. However, Sebastian wasn't taking no for an answer and kissed her hard, only to be pushed back by Holly so forcefully that he fell out of the helicopter! Horrified that she'd killed him, Holly quickly left the island and told no one what happened.

About month later, in Springfield, Holly was shocked to come face to face with a very much alive Sebastian! Holly was certain that he'd come for revenge, but he surprised her by revealing that he was now a cured, and changed man and wanted to start a new life for himself in Springfield. His new life included getting a position at Spaulding Enterprises and he ingratiated himself with Alan Spaulding by bailing him out of prison in exchange for a job. As he'd hoped, he got into Alan's good graces and was offered the co-presidency of Spaulding Enterprises. However, that arrangement didn't sit well with the current president, Olivia Spencer, who'd fallen out of favor with Alan. In the meantime, Holly and Sebastian agreed that it would be best for them to stay away from each other. However, despite what she said, Holly felt pangs of jealousy when she saw Sebastian speaking with Beth Raines. She then surprised Sebastian by offering to do a story on him, about how a man could change. Although she claimed her interest was strictly professional, neither Sebastian nor Beth were so sure. Later, at a small Spaulding function, Holly accepted a business deal with Alan and used the opportunity to make Sebastian jealous.

Meanwhile, Sebastian let Blake in on his plan: he wanted to take over Spaulding Enterprises, something Roger always wanted. Blake was intrigued and wanted to help but Sebastian hesitated since his plan depended on having Alan trust him implicitly, and Blake couldn't help him do that. Later, a crafty Blake created a scene, giving Sebastian the perfect opportunity to show Alan his loyalty. Sebastian would turn out to be as dangerous as his father. After hearing that Alan put a bounty on the fugitive Harley Cooper's head, Sebastian offered to locate Harley and Alan's son, Gus. Weeks later, Sebastian received another order from Alan--permanently silence a Dr. Wallace. Intrigued as to why Wallace was more important than finding Harley (who had supposedly killed Alan's son, Phillip), Sebastian was sure there was a connection between the two when Harley showed up at the same location as Wallace. Unfortunately, Sebastian wasn't able to find out the connection since the next day he spotted Harley and Wallace together on the street. Instinctively knowing that the pair should not be talking, Sebastian ran down Wallace!

After getting the runaround from Alan, Sebastian finished the job of permanently silencing Wallace by injecting him with a fatal drug. Later, Sebastian found a note that Wallace left for Gus, implicating Alan as the killer. At the same time, an injured Gus found himself in Sebastian's sights. When Alan called, Sebastian delivered the good news that Gus was in fact alive but later, unwilling to take any chances, Gus knocked Sebastian out, not wanting him to discover Harley's location. Later, when Sebastian came to, he inadvertently dropped the incriminating note for a nurse to find. Before leaving New York, Sebastian tipped off the police to Gus's whereabouts. Soon after, back in Springfield, Alan was forced to confess that he killed his son and was put in prison. However, Sebastian broke him out of jail; all he wanted in return was Alan to sign over Spaulding Enterprises to him. Alan resisted but Sebastian remained firm. Later, when a cop arrived, Sebastian covered for Alan, only to be knocked unconscious by him and locked in a closet. Sebastian quickly broke the door down and got out.

Luckily, or so he thought, Sebastian came across Alan's granddaughter, Lizzie, and lured her onto the Spaulding jet with him. Although he planned to use her for ransom, the teenager proved to be so annoying that, in frustration, he let her go. Finally realizing that the town wasn't worth all this aggravation, Sebastian wasted no time getting out of Springfield.