Schuyler Joplin arrived on the scene as the new biology teacher at Llanview High School, where the young teacher quickly caught the eye of student Starr Manning. Starr was stunned to learn that Mr. J was actually Schuyler Joplin, the son of her obstetrician Leah Joplin, who had committed suicide after believing she was responsible for the death of Starr and Cole's baby. Starr admitted to Schuyler that her father Todd Manning plotted with his mother to steal her baby. Schuler admitted to Starr that he blamed himself for his mother's death because he used to be a drug addict. Starr and Schuyler shared a hug, and Cole barged into the classroom and ordered Mr. J to get his hands off of Starr. When Starr explained who Schuyler was, Cole lashed out at Schuyler and said that Dr. Joplin was responsible for his baby's death.
When questioned by authorities about his mother's death, Schuyler denied knowing anything about the plot to kidnap Starr's baby and said his mother would never have gone along with such a scheme. But when he was alone, Schuyler read a letter to him from his mother in which she admitted that she had gone along with Todd's plot to keep Schuyler from being sent to prison for stealing drugs while he was a junkie. When school authorities discovered that drugs were being dealt on campus, Starr admitted to Schuyler that she knew someone who was hooked on drugs - although she didn't tell him that the person was Cole. Schuyler later helped Starr work through her conflicted feelings about testifying against her father, and his words eventually helped her decide that she didn't want to see her father go to prison. Schuyler also wanted to protect his mother from her crimes, and at her graveyard he burned the letter that would have proved Todd's guilt.
Starr and Schuyler continued to grow closer. Starr admitted to Mr. J that she felt an overwhelming connection to her cousin Jessica's new baby Chloe, unaware that the baby was actually her daughter Hope. When Schuyler ran into a stoned Cole in the hall at school, he called Cole on being high but said he wouldn't turn him this time. Cole assumed Starr had ratted him out to her favorite teacher, but Starr later told Cole that Schuyler knew all about addition because he was a former drug addict himself.
At a high school dance in March, Starr leaned on Schuyler because she was upset about Cole's drug use. Schuyler told Starr about destroying his mother's letter, and Starr - realizing how much she and Schuyler were alike - leaned in and kissed Schuyler, just as Cole came around the corner and saw them. Cole pulled Schuyler off of Starr and tried to strangle Schuyler. When the vice principal arrived on the scene, Cole told her that Mr. J had kissed Starr and then outted him as a drug addict. But Starr admitted that she was the one who kissed Schuyler, causing Cole to storm off and get in to a car accident in which Matthew Buchanan was paralyzed. Later Schuyler told Starr that he had been suspended indefinitely from school because of the incident. When Starr said she knew Schuyler felt something for her, he reminded her that he was her teacher and could be nothing more.
One day, Starr showed up at Schuyler's apartment to find him in the shower. When Schuyler came out, clad only in a towel, he ordered Starr to leave. But she began taking her clothes off, saying how she wasn't a child and wanted to be with Schuyler. After nearly getting caught together by Cole, Schuyler told Starr there was no way he would ever be with her. Devastated, Starr stormed out, still buttoning up her blouse, and Cole spied her from the hallway. Schuyler later returned home to find a love letter from Starr, which he first threw away but later read. He was writing a note back to her when Todd burst into his apartment and began reading the letter. Todd and Schuyler faced off, with Schuyler calling out Todd for his plot to kidnap Starr's baby with his mom's help. Todd then revealed that Cole had told him about what happened between Starr and her teacher, and he slammed Schuyler's face into the door before leaving.
Stacy Morasco, Schuyler's ex-girlfriend, invited herself to stay with Schuyler after her sister Gigi found her in bed with Gigi's boyfriend, Rex Balsom. Schuyler eventually admitted how much he loved Stacy and kissed her. But Stacy told a rejected Schuyler that she wanted to be with Rex and believed that fate had brought her to Llanview to be with him. Schuyler began to suspect that something wasn't right with Stacy's plans to donate her bone marrow to Gigi and Rex's son Shane, who was suffering with leukemia. When he showed up at Stacy's hospital room, he saw Stacy throw something in the medical waste bin. When he was alone, he retrieved a bag of blood from the bin that had Stacy's name on it. Little did Schuyler know that Stacy's blood had been switched by Roxy with the blood of the real donor, Rex's mystery father. Schuyler confronted Stacy with the blood and didn't believe her feeble excuse. Schuyler presented the blood to Rex in dramatic fashion and told him that Shane didn't get Stacy's bone marrow, but Rex thought Schuyler was crazy. Schuyler then threw Stacy out of his house. Determined to get proof, Schuyler used his former teaching privileges to gain access to the hospital lab and run tests on Stacy's blood.
Schuyler went to Gigi's home and told her that he had seen Stacy throwing away the bag of blood she supposedly had donated to save Shane. Schuyler shared with Gigi his suspicions that Stacy was lying about being the donor, and Gigi knew that if they could prove that, then she could tell Rex the truth and reunite with him. But when Schuyler and Gigi showed up at the hospital to get the lab results on Stacy's blood, lab technician Kyle Lewis doctored the file to show that she was a match. Schuyler knew Kyle was in cahoots with Stacy, having seen the pair conspiring at his apartment, although he didn't know why. Gigi got into a fight with Stacy and ripped out some of her hair, which Schuyler took to another lab to get tested. Those results proved that Stacy was not Shane's donor, but Gigi was reluctant to tell Rex until she could find out who the real donor was in case Shane needed another transfusion. While Schuyler was subbing for Gigi at Rodi's, Roxy came in and got to talking to Schuyler about Stacy. She nearly let it slip that Stacy wasn't the one who donated her blood to save Shane, and Schuyler could tell that Roxy knew the truth and was scared. He told Gigi that Stacy had obviously blackmailed Roxy just like she had blackmailed Gigi. But when Gigi tried to get Roxy to open up, she refused to tell Gigi what Stacy was holding over her head.
Gigi tried to find out who the real donor was by flirting with Kyle Lewis, but he rejected her advances and said he would only reveal what he knew if Gigi could get Natalie and Jared to drop the blackmailing charges they had filed against him. Gigi asked Natalie and Jared to drop the charges and, with some prodding from Schuyler, told them the truth about what Stacy had done. They all agreed that Gigi should tell Rex the truth, which she did. At the same time, however, Stacy was telling Schuyler that she and Rex had slept together that very day. Schuyler struggled with this knowledge, especially after he realized that Rex had not admitted to Gigi that he had slept with her sister. When Rex and Gigi reunited, Schuyler told Rex that he knew he had slept with Stacy but kept quiet to Gigi. Rex and Gigi, meanwhile, hatched a plan to bring down Stacy, who had stashed an extra bag of blood from the real donor in a refrigerated fur storage facility. After Stacy's lies were exposed, and she was forced to hand over the bag of blood to Rex, Schuyler tried to comfort her but Stacy rejected his help. After Stacy fell down a flight of stairs during an altercation with Gigi, she discovered she was pregnant with Rex's child and told Rex the good news in front of Gigi, who was stunned to learn that Rex had lied to her.
Gigi and Schuyler grew closer as Gigi struggled to deal with the fact that her sister was having her boyfriend's baby. Schuyler confided in his co-worker at the drug treatment center, Rachel Gannon, about his attraction to Gigi and struggled to keep his feelings in check. One day, however, after Rex warned him to stay away from Gigi, Schuyler bit the bullet and kissed Gigi. Gigi was stunned, and Schuyler was forced to backtrack and say that it was a mistake that would never happen again. Gigi told Rex about the kiss and he went ballistic, ordering her to never see him again. Later, Rex encouraged Schuyler to leave town, and Schuyler told Gigi that he was considering it because he felt he couldn't be just friends with her. But Gigi told Rex that she would never cheat on him and Rex agreed that she and Schuyler could remain friends.
After Stacy suffered a miscarriage, she and her friend Kim Andrews concocted a plan for Stacy to conceive another baby that she could pass off as Rex's. After two other failed attempts with other men, Stacy set her sights on Schuyler. She plied an unsuspecting Schuyler with a drug provided by her friend Kim, which made Schuyler woozy. Schuyler started making out with Stacy, imagining that she was Gigi, but stopped abruptly when he realized that Stacy was in his bed. Schuyler said he only wanted to be with Gigi, and he ordered Stacy to get out. After discovering that Rex and Gigi had been fighting about Schuyler's role in Gigi's life, Kim and Stacy hatched a plan to break them up for good. Kim asked Schuyler out on a date and made out with him in full view of Gigi, making her jealous enough to storm out of the movie she and Rex were watching. Kim encouraged Schuyler to make the moves on Gigi, since he was obviously attracted to her, but Schuyler balked when he realized what Kim and Stacy were trying to do. Schuyler continued to find himself drawn to Gigi, however. After Rex bailed on a couples counseling session with Gigi to take an out-of-town assignment, Schuyler invited Gigi to go with him to a concert for Gigi's favorite band using tickets Kim had given Schuyler. Schuyler then stepped in for Rex for the Halloween contest and played Batman to Shane's Robin, and the trio won. Later, after Gigi told Schuyler he had been accepted into medical school, Schuyler planted a kiss on Gigi, and Gigi didn't back away. She admitted to Schuyler that she had feelings for him, and that was the reason she and Rex had scheduled the counseling session.
Schuyler walked in on Stacy adjusting a pregnancy pad, which she was wearing so it would appear she was further along with her pregnancy than she really was, and accused Stacy of faking her pregnancy. Kim told Schuyler that Stacy had lost Rex's baby but then got pregnant by him. Stacy then admitted that she had drugged Schuyler and said she lied when she told him that they never had sex. Schuyler was going to tell Rex that the baby wasn't his, but then Kim and Stacy convinced him that Gigi would never give him the time of day if she learned that Schuyler had slept with Stacy and gotten her pregnant. Schuyler confided everything to Rachel, who urged him to come clean to Gigi. But after Gigi moved out of the carriage house to sort out her feelings, Schuyler seized the opportunity and got even closer to Gigi. The two spent Christmas together at Viki's cabin, and on New Year's Eve Schuyler and Gigi made love for the first time. Schuyler told Gigi that he loved her, although the afterglow was short-lived because Shane barged in and figured out that his mom had slept with Schuyler. Schuyler stood by as Rex confronted Gigi, who confessed that they had slept together and told Rex she wanted to pursue a relationship with Schuyler. Roxy kicked Schuyler out of the Angel Square Hotel because he had come between Gigi and Rex, and Schuyler convinced Rachel to share an apartment with him.
When Kyle Lewis walked into a hospital room and overheard Schuyler arguing with Stacy about her unborn baby being his and not Rex's, Stacy and Schuyler convinced Kyle not to say anything to Rex since he would be breaking patient-doctor confidentiality. Stacy and Kim convinced Schuyler to steal a drug called Oxytocin from the hospital that would induce labor, allowing Stacy to deliver the baby ahead of schedule and pass it off as Rex's. When Schuyler learned that Stacy was going to name Kim as the guardian of her baby if anything happened to her, Schuyler forced Stacy to name him as the guardian in exchange for receiving the drug. But when Stacy faked going into labor and was rushed to the hospital, Schuyler refused to administer the drug and destroyed it. When Kim went after Schuyler to change his mind, Stacy was kidnapped by one of Mitch Laurence's minions and taken to a hiding place on Llantano Mountain where Mitch was. Schuyler headed up to Viki's cabin on Llantano Mountain, where Gigi was staying, so he could tell her the truth about him being the baby's father. But he slid off the icy road before he could get there and headed off on foot. Rex and Oliver went off to look for Stacy and came upon Schuyler's abandoned car. Rex found Stacy's will and was shocked to see Schuyler listed as the baby's guardian. When Rex finally found Schuyler, Schuyler admitted everything -- that he was the father, not Rex, and even told Rex about the plot to administer Stacy a drug to induced labor early. Rex, Schuyler and Oliver all were shocked when Gigi showed up, carrying Stacy's sickly newborn baby, whom Gigi had delivered after Stacy had been kicked out of Mitch's lair and gone into premature labor. Gigi fell through a sheet of ice and nearly drowned before Rex saved her. Stacy then arrived and fell into the ice as well. Gigi and Schuyler took the baby to the hospital as Rex and Oliver stayed behind to rescue Stacy, but Stacy was too weak to hang on and drowned. After learning about Stacy's death, Gigi vowed to watch over Sierra. When the baby needed surgery, Schuyler admitted to Gigi that he was the baby's father. After learning about all that Schuyler had done to keep the truth from her and Rex, Gigi told him they were through and then filed for legal custody of the baby. After the hospital realized the Oxytocin was stolen, Schuyler had to go before an ethics review panel but was cleared of any wrongdoing thanks to the efforts of Rachel and Téa.
Schuyler brought baby Sierra home with him, believing the child was his. One of Mitch's disciples, Allison Perkins, pretended to be the court-ordered social worker and drugged Schuyler before kidnapping the baby, who Allison said was still important to Mitch even though the baby wasn't Rex's child. Schuyler was forced to tell Téa that the baby was kidnapped but pleaded with her not to report the police, fearing what Allison would do to the child. Schuyler was instructed by Allison to switch places with Kyle Lewis on medical rotation at Statesville Prison and to help Mitch escape from the prison. When Mitch was brought into the prison's medical clinic, feigning a seizure, Schuyler injected him with a drug that he said would kill him if he didn't hand over Sierra. Mitch summoned Allison, who arrived at the prison with the baby and a gun. Inside the locked medical room, Allison revealed that baby Sierra was actually Mitch's granddaughter because Schuyler was Mitch's son, not Rex! Allison explained that the baby Roxy had delivered (Schuyler) was very ill when he was born so Allison switched the baby with a healthy newborn (Rex) who had been abandoned by his parents and brought to the hospital. Baby Schuyler made a full recovery but it was too late to reverse the switch, so Allison told her sister Leah that she had given birth to the baby but didn't want it and asked her sister to raise the baby. Schuyler refused to administer the antidote that would save Mitch, instead throwing it under the bed and walking out of the locked room with Sierra in his arms. Schuyler then got his second shock: police officer Oliver Fish told him that he was Sierra's father, not Schuyler, and showed him a paternity test to prove it. Despondent, Schuyler handed over the baby and then went to Gigi, telling her he had found Sierra and convincing her to go with him. At Viki's cabin, Schuyler confessed that Officer Fish was Sierra's father and then pulled out Allison's gun, telling Gigi she was all he had left. Rex and Bo arrived and tried to talk Schuyler into putting down the gun, but Schuyler pointed the gun at Rex and fired. Bo jumped in front of Rex and was shot, and Schuyler was arrested. At the police station, Schuyler told Téa what Allison had told him about his true parents. Roxy, who had just learned the truth herself, told Schuyler she would stand by him. Téa prepared to enter an insanity plea, but after seeing Gigi enter the back of the courtroom, Schuyler stood up and declared his guilt. He said goodbye to Sierra and was carted off to Statesville, but not before telling Rex that he never stood a chance with Gigi.