Nikolas knows that the ring and the dress belonged to Laura only. He senses the bench means something connected to Laura, too. Nikolas becomes worried and goes to see Laura, wanting to know had there ever been anything between his uncle and her. She tells him the same half-truths that Stefan has told him, but Nikolas is unhappy with her answers and leaves. After reading an invitation to Stefan and Katherine’s Bacchanalia, with a note from Stefan that he his finally giving Nikolas the mother he deserves, Laura decides its time to come home. She arrives during the ball and goes to the guest house to find a secret passage to the mansion.
Luke and Alexis have hatched a plot to get rid of Helena. Luke has loosened the parapet railing and Alexis is going to lure Helena there and get her too close to the railing so she will fall.
Katherine is devastated when she sees Laura dressed in the same way as herself and Laura tells her the ring and the dress was hers alone. Katherine locks her in the guest house but Laura finds the secret way out. Stefan and Laura have a conversation where Laura finally admits she knew all along that Stefan was her son’s father. She warns Stefan that he is playing with fire and will destroy them all if he doesn’t get rid of her trunk and all the contents. She tells Stefan if he really loves Katherine to let her be herself. Katherine finds the portrait of Laura and confronts Stefan. He denies everything, telling Katherine he loves only her. Laura come upon them on the parapet and suddenly Katherine senses the truth that Stefan is Nikolas’s father. She backs away, the railing gives way and falls off the parapet. Stefan makes Laura leave before she is seen.
Katherine is taken to General Hospital with numerous internal injuries. While Stefan is in the corridor, he does not see Helena slip in and out of the trauma room where Katherine is being treated. Katherine dies moments later. A shaken Stefan sobs, telling Katherine that he loved her and never meant for her to be hurt.
Stefan is soon arrested for murder because Luke deliberately used Stefan’s letter opener to loosen the parapet and dust from the mortar is on the opener to frame him. Katherine had also made Stefan the beneficiary of her will and that makes the PCPD suspicious. Katherine’s “ghost” appears to Stefan, helping him get through the grieving process and to come to terms with his feelings for Laura.
Stefan and Laura grow close as the conspirators try to keep secret that it was she who was on the parapet that night with him and Katherine. Laura grows closer to Nikolas with Stefan’s approval. Alexis tries to get Laura to admit she was there but not until Nikolas begs her to testify for his uncle does she go see Alexis. Stefan is shocked and afraid of what Laura will reveal on the witness stand. Laura had tried to tell Luke what she was going to do before she testified but he wouldn’t listen. He is in the courtroom when Laura testifies she was with Stefan that night. DA Jensen tries to make it seem like there was something between Laura and Stefan. When Jensen asks her point blank if she had ever slept with Stefan, Laura says no. Luke gets up and leaves. Laura’s testimony saves Stefan but breaks up her marriage. Luke knew she was lying and figures out that Nikolas is Stefan’s son. Luke leaves town.
Stefan and Laura grow closer. Helena is arrested for Katherine’s murder when Luke and Alexis fake evidence pointing to her. The big shocker comes when Katherine Bell shows up alive and testifies for Helena saying that she had saved her life. Stefan doesn’t trust this Katherine but she insinuates herself into Nikolas’ life. Both Stefan and Laura wonder what she really remembers about that night. They know she’s a walking time bomb. Luke also threatens to tell what he knows and moves out. Laura wants to tell Nikolas the truth but Stefan wants Nikolas to have what he couldn’t: the Cassadine title. He also fears that Nikolas will hate him. When Katherine remembers the truth she tells Nikolas and after a confrontation with Stefan, Nikolas embraces the idea of being Stefan’s son.
Stefan and Laura begin dating and having dinner most evenings at his home. He wants their relationship to progress, but agrees to give Laura the time she needs to get over losing Luke. They make plans to go to Paris, but that night Lucky dies in a fire in his apartment. Laura has a breakdown that Stefan helps her through, even saving her life by pulling her from the path of a speeding train. Lesley doesn’t like Stefan but she see how much he cares for Laura.
Helena goads Laura so much about causing Lucky’s death that she has a breakdown. Stefan convinces her to spend the summer at his country home, so she can heal emotionally. While she is there, Stefan arranges for Helena to be given a drug that paralyzes her. He moves Helena to Wyndemere on the pretense of taking care of her like a good son. A healed Laura returns home and becomes the one providing emotional support.
Katherine wants to be a Cassadine and seduces Nikolas, later pretending to be pregnant to keep him tied to her. On the eve of their wedding, Helena (who had been faking her paralysis since Faison had given her an antidote) sends Laura information proving Katherine was not pregnant and is, in fact, sterile. Laura confronts Katherine, and, a few minutes later, is seen looking over the parapet at the body of Katherine lying dead on the ground. Stefan fears Laura had a blackout and confesses to the crime to keep Laura out of prison or a mental institution.
Alexis discovers that Stefan has been duped. Nikolas is not his son but Stavros’ after all. Stefan is heartbroken. Laura asks Luke for a divorce and then goes to Wyndemere and makes love to Stefan. Alexis tells Nikolas the truth and he confronts a disbelieving Laura. Stefan confesses that he just found out but Nikolas doesn’t believe him because of all of his other lies. Laura defends him and tells him she will never leave him. Stefan and Laura discover it was Helena who murdered Katherine. She is arrested, but not without a price. Stefan had lied to Laura about drugging his mother and she finds out the truth. Laura backs away from Stefan for a while. Luke comes calling again and Laura is torn between the two men, but reconciles with Stefan.
Stefan discovers that Lucky did not die in the fire but that Helena and Faison had kidnaped him. Stefan doesn’t tell Laura anything, afraid that if he can’t bring Lucky home it will devastate her all over again. Luke is suspicious of Stefan and follows him. He overhears some conversations and comes to the wrong conclusion that Stefan and Helena are playing a game with Lucky, kidnaping him back and forth. Luke tells Laura this and she will not listen to Stefan.
Luke and Laura leave on a wild goose chase Helena takes them on to find Lucky. Stefan follows trying to get Laura to let him help. She rebuffs him until he gives up on her. Lucky is brainwashed and doesn’t want to have anything to do with anyone. He punches Luke out when he see him for the first time. Stefan catches Helena on her airplane and confesses all his feelings for her and then, to her surprise, has her arrested. Neither Nikolas nor Laura will believe Stefan or Alexis when they tell them that Stefan had nothing to do with Lucky’s kidnaping. Nikolas cuts himself off from Stefan. Lucky won’t have anything to do with his parents. Helena has poisoned him against them.
Getting nowhere with Lucky, Laura appeals to Stefan after having a nasty run-in with Helena. Stefan promises that if he finds out anything he will tell her. Helena knows Stefan is getting too close to the truth so she plans to get rid of him. Stefan convinces Andreas to tell him what she is going to do and help him. Helena poisons him but Stefan has taken an antidote and fakes his death, making sure to frame Luke for the deed.
Chloe Morgan has been having psychic dreams because of a brain tumor and “sees” Stefan’s murder. Helena becomes suspicious of the woman and tries to kill her. Stefan is having the time of his life in Europe, waiting for Helena to make the wrong move. He finds out about Chloe’s dreams and sends Jax on a wild goose chase looking for his lost love, Brenda. Stefan kidnaps Chloe and pretends that Helena, who he says kidnaped him and left him on this island with no way off, was her kidnapper, too. Chloe refuses to give up and continually tries to escape, much to Stefan’s dismay. He comes to admire her tenacity and spirit. Without her medication Chloe has her dreams. Stefan urges her to try and help him defeat Helena through her dreams.
Luke is acquitted of Stefan’s murder when Felicia confesses that she was with him the night Stefan was murdered. Helena cuts off Nikolas’ funds to try and control him and Stefan sees that Nikolas gets money. Stefan is starting to have romantic feelings for Chloe, then finds out that she has been having episodes of blindness. He feels guilty and arranges for them to “escape” from the island. Everyone is happy to see them though some doubt his explanation that Helena kidnaped them. Chloe happily believes him until she “sees” him goading Helena in a dream where he confesses to kidnapping her and pinning it on his mother. Chloe is furious and doesn’t want anything to do within Stefan. Nikolas turns against him once again.
Stefan is determined to find out Helena’s agenda. His mother is continually goading him about how wonderful his brother Stavros was. Helena has an underground laboratory under the sub floor of General Hospital where she has Stavros cryogenically frozen. Luke has stolen a pair of CD’s from a safety deposit box in Turkey that belonged to Helena. When he can’t read the encrypted CD’s he sells them back to Helena. She doesn’t know that Luke made a copy. Helena is using the Ice Princess to keep Lucky under her power and to do her bidding.
Stefan tries to get Luke to let him help decode the CD’s but Luke won’t have it. Stefan tries to steal them, only to get caught. Helena threatens Tony Jones with the death of his son, Lucas, if he doesn’t bring Stavros back to life. Tony is successful and Stavros lives once again. Helena is not happy when Stavros immediately asks where Laura is. Stavros wants his wife and son back and vows to destroy Luke and his brother, Stefan. He introduces himself to a few people by the name of Lucian Cane, being careful not to let anyone see him that might be able to identify him. He charms Chloe and tries to seduce Gia.
Jax returns and warns Stefan to stay away from Chloe. Jax has brought Alexis’ sister, Kristina, to her. They haven’t seen one another since Helena killed their mother. Stefan continues to pursue Chloe and asks her to marry him. She refuses but starts to soften toward him. When Chloe sees Stavros’ picture in a photo album in Stefan’s study she realizes who Lucian really is. Unfortunately, Stavros had suspected her suspicions and confronts her. Stefan finds her lifeless body behind the curtains and tries to revive her. Jax and Alexis find Stefan crying over Chloe’s dead body. Jax immediately thinks he has killed her.
To cheer Stefan up after Chloe’s funeral Alexis takes him to meet Kristina. Stefan is overjoyed to find out he has another sister. Stefan is arrested for Chloe’s murder when preliminary DNA results show he is the killer. Laura is one of the few people who believes he is innocent and she comes to see him in the jail. He asks her to get the CD’s from Luke and help him try to break the code so they can know what Helena is doing. She agrees and they find out that the CD’s carry the instructions on how to revive a cryogenically frozen person. Stefan figures out that all the things he thought he was imagining about Stavros was, in fact, true and that his brother was alive. And it is the only logical reason the DNA results pointed to Stefan since his brother would have similar DNA components.
At first Stefan gets the upper hand with his older brother, but Stefan ends up tied up in the laboratory. Alexis, Luke, Laura, Roy, Gia, Nikolas, and Lucky are also trapped in the lab as Helena plots to take over the world. Stavros doesn’t care about anything but Laura, wooing her with flowers, gowns, and a replica of their bedroom. Laura spurns him and after Luke and Stavros battle with such dangerous weapons as pillows and dresses, Luke and Laura get away. Stefan and Lucky trigger the fail-safe in the computer and the complex shuts down as everyone but Stavros escapes. Strangely, he opts to fall down a dark hole than to listen to more of Luke’s bad jokes.
Helena is arrested and Stavros is presumed dead. Stefan decides that Nikolas can run the Cassadine empire all by himself and he signs it all over to him. While reading his diary from years past, Stefan realizes he has never followed his dreams. He announces to his family he is leaving town to find himself. None of them want him to go but wish him well. Stefan Cassadine, the most interesting, multi-faceted character on daytime leaves to go to Milan.
In 2003, Stefan returned to Port Charles to ask Nikolas to marry a young woman to restore the Cassadine fortune. Stefan tried to manipulate the situation and failed. He also became the target of Luke Spencer again, who murdered Stefan by stabbing him and pushing him off a cliff.