Kyle Lewis first appeared in Llanview when the Buchanan family needed tests run to determine whether David Vickers was the late Asa Buchanan's son. The tests ultimately proved that David was actually fathered by Asa's son Bo Buchanan. When Shane Morasco was diagnosed with leukemia, Kyle oversaw bone marrow testing for possible matches and discovered that an anonymous donation provided by Shane's grandmother, Roxy Balsom, was a match. Kyle agreed to harvest stem cells from the anonymous donor, who was convalesced in a nearby long-term care facility. Kyle realized that the donor was Rex's believed dead father, but he agreed to keep the person's identity a secret and to pretend that Shane's aunt Stacy Morasco was the donor. Later, Kyle bribed Roxy into giving him a room rent-free at the Angel Square Hotel.
Kyle was shocked to run into Llanview Police Officer Oliver Fish, who was investigating a string of murders that appeared to be connected to the 1993 gang rape of Marty Saybrooke at the KAD fraternity house at Llanview University. Kyle and Oliver both were members of the fraternity many years after the rape, but had not been in contact since graduating.
Kyle ran a DNA test for Natalie Buchanan and Jared Banks that confirmed their suspicions that Natalie's sister, Jessica Brennan, had switched her own stillborn baby with a healthy baby belonging to Starr Manning and Cole Thornhart while under the influence of an alternate personality. Knowing that the truth would devastate Jessica, Natalie and Jared decided to keep quiet about the baby switch. But when Starr and Cole requested a similar DNA test to determine how their baby had died, Kyle realized that the babies had been switched and told Natalie and Jared that he would reveal the secret if they didn't pay him $100,000 within 24 hours. Later, at Natalie's bachelorette party, Kyle masqueraded as a male stripper, intimidating both Natalie and Roxy with his knowledge of their secrets.
Tired of waiting for Natalie and Jared to pay up, Kyle went to Todd Manning's house to see if he could get more money out of Todd for information about his grandchild. There he ran into his sister Rebecca Lewis, who had been involved with Todd many years ago but was now helping Todd's cousin Powell Lord carry out a series of murders intended to make Todd pay for orchestrating Marty's gang rape. When Kyle told Rebecca that Todd and Marty's grandchild was alive, Rebecca kidnapped the baby from Llanfair for Powell to use as leverage in his vendetta against Todd. Kyle stayed behind at Todd's to watch after Jack and Sam and was there when Starr and Cole returned home from the prom. As Kyle attempted to leave he was stopped by Officer Fish, who brought him to the station for questioning. There, Kyle was charged with bribing Natalie and Jared, who came clean to their family about the baby switch after the kidnapping. Kyle phoned Stacy and bribed her into paying his bail. After Gigi and Schuyler figured out that Stacy had faked being Shane's donor with Kyle's help, Gigi tried to find out who the real donor was by flirting with Kyle. But Kyle 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. Natalie and Jared dropped the charges, pressuring Kyle to reveal the name of the donor. Kyle claimed to have forgotten the donor's name but took Natalie and Jared to the clinic where the donor was. When they arrived, they discovered that the donor had died several months before, and Kyle admitted that he had drawn extra blood and given it to Roxy.
At the diner one day, Kyle overheard Cristian talking on the phone with Layla about her dating Oliver, and Kyle told Cristian that Layla was going to get hurt. Kyle told Cristian that Oliver wasn't the man he was making himself out to be and said Cristian should warn Layla not to date Fish. But when Cristian confronted Oliver, Fish said Kyle was just jealous because he wanted Layla for himself. When Cristian went to Kyle's room at the Angel Square Hotel, he saw a note slipped under the door addressed to Kyle and read it. The note was from Fish, who asked Kyle to back off and said that he wasn't the guy he knew in college anymore. When Kyle appeared, Cristian admitted to reading the letter but Kyle refused to give Cristian any information, saying that what happened between him and Fish was between them. Pressed further, Kyle told Cristian that Fish was with someone in college but broke it off because he cared more about what people thought.
Roxy Balsom bonded with Kyle over a bottle of booze, knowing that Kyle was upset over the cute guy in the picture that Kyle kept in his wallet. Kyle said the guy wouldn't admit the truth about himself, but Roxy said some people lie to keep their worlds from spinning out of control. After learning that Kyle had told Roxy that he and Oliver were involved in college, Oliver confronted Kyle and the two got into a heated exchange in the ally behind the Buenos Dias Café. Kyle accused Oliver of being scared to accept that he was gay and told Oliver that he still loved him. Oliver denied being gay, but Kyle pressed him to admit that they meant something to each other, and the two ended up in a passionate kiss. Cristian oversaw the kiss and confronted Fish, who claimed that Kyle had been stalking him. Cristian could tell Fish was lying and told him to come clean to Layla, or he would be forced to.
Oliver ran into Kyle at the gym and told Kyle that he and Layla were sleeping together. Kyle tried to break through to Fish, reminding him of the times they shared in college and all the times Fish used to tell Kyle that he loved him. Kyle reached out to Oliver, who took his hand, but then Cristian appeared and Oliver immediately pulled away. Kyle covered for Fish, telling Cristian that Fish was in love with Layla and that Fish was just trying to let him down easy. Kyle approached an attractive guy at the gym named Nick and gave out his number, which made Oliver jealous enough to go up to Nick and warn him to stay away from Kyle. On their date, Kyle filled Nick in on his ex, and the two realized that Oliver had warned Nick to stay away from Kyle.
The charges against him dropped, Kyle was able to get back into medical school and became a trauma intern at Llanview Hospital. When Nick arrived at Kyle's apartment with champagne to congratulate him on getting back into school, he was disappointed when Kyle brushed him aside, saying he had to leave for work. Nick asked if Kyle still had feelings for Oliver, but Kyle brushed off Nick's suspicions. While at the hospital, Kyle ran into Fish and learned that Fish had finally come out to his parents. They recalled how Oliver's mother had once walked in them in bed together, which had prompted Fish to break it off. Fish admitted that he only got the nerve to come out after he had drunken sex with a girl, although Fish didn't tell Kyle that the girl was Stacy. At the Angel Square Hotel, Kyle and Nick shared a kiss goodbye after spending the night together and Kyle ran into Oliver's parents. Oliver's dad blamed Kyle for corrupting his son, while Kyle said that Oliver looked to his dad as a hero and that it would kill Oliver to lose his parents forever.
Oliver hoped to resume a relationship with Kyle after coming out, but Kyle said it was too late and that he was already seeing Nick. Kyle was surprised in October 2009 when Nick asked to marry him as part of a mass commitment ceremony being staged in Angel Square Park to raise awareness of the need for gay marriage rights. Kyle accepted Nick's proposal, deciding it was good for the cause, although he began to question it after discovering that the goal was to legitimize the marriages after Dorian Lord was elected mayor. The day before the wedding, Fish told Kyle he loved him and said he wanted a chance to have a relationship with him, but Kyle said he was afraid a relationship with Oliver would mean a life of living in the closet. As the commitment ceremony was about to begin, Fish confronted a group of protesters and, on live television, admitted he was gay. Kyle decided right then and there that he couldn't go through with marrying Nick, and he and Oliver agreed to begin dating.
Kyle and Oliver slowly got to know each other once again and planned for their first date, which was interrupted when Oliver was called away on police business. When they prepared to make love for the first time since college, they were interrupted by news that Kyle's ex, Nick, had been beaten up by a group of gay-bashing thugs. Oliver was supportive of Kyle as he helped Nick recover, but became suspicious when Nick said he had no place to go and moved into Kyle's studio apartment. Oliver and Kyle got in an argument about Nick, and Kyle later learned that Nick was playing him and wanted to get back together. Kyle rejected Nick's advances and went after Oliver, finding him just before midnight on New Year's Eve. They rang in the start of 2010 by making love. One day at the hospital, Kyle walked into a 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. After Rex hired Oliver to look after Stacy and her unborn baby, who were being threatened by Rex's evil father Mitch Laurence, Oliver confided in Kyle that he and Stacy had made love. Kyle told a stunned Oliver that he could be the father of Stacy's baby, since she had lost Rex's baby and gotten pregnant around the same time they had sex. Kyle and Oliver confronted Stacy and her pal Kim, but they denied that Oliver was the baby's father and stuck to the lie that Schuyler was the daddy. Though they threatened to tell Rex and Schuyler the truth, they backed down after Stacy and Kim said they would have Kyle thrown out of medical school for breaking doctor-patient confidentiality. Oliver wasn't sure what to believe, but Kyle said Stacy couldn't be trusted and could be blackmailing Schuyler. Oliver said they would have to wait until the baby was born to learn the truth, and he told Kyle that he wasn't ready to be a father yet anyway.
After a pregnant Stacy was kidnapped by one of Mitch's goons, Kyle confessed to Roxy that the baby Stacy was carrying wasn't Rex's. Stacy delivered a baby girl, named Sierra Rose, before falling into a sheet of ice and drowning. At the hospital, Sierra needed to have emergency heart surgery and Schuyler revealed to Gigi that he was Sierra's father. Kyle urged Oliver to have a DNA test to determine if he was actually the father, but Oliver refused. Kyle had the test done anyway and presented Oliver with the sealed envelope containing the results, but Oliver lashed out at Kyle for breaking the law and refused to open the letter. Kyle was working in the medical clinic at Statesville Prison when Schuyler came in and relieved him. Kyle returned home to discover a despondent Roxy tied up on the sofa by Allison Perkins, who had kidnapped Sierra. Allison tied up Kyle as well before getting a call from Mitch and taking off with the baby. Fish arrived and freed them both. When Kyle told Fish that Allison had kidnapped Sierra, Fish opened the paternity test and learned he was Sierra's father. Fish told Schuyler the truth and was united with his daughter. He and Kyle brought the baby home and prepared to raise her. Fish stood up in court and affirmed he was Sierra's biological father, and the court awarded him full custody. Fish and Kyle told both Gigi and Roxy that they would always be a part of Sierra's life. Rex, who had just discovered he wasn't Roxy and Mitch's son after all, questioned Kyle about the stem cells that saved Shane's life. Kyle confirmed that the stem cells came from Mitch. Kyle ran a blood test that confirmed that Mitch was not Rex's father, but Kyle explained that non-relatives often are matches for stem cell recipients. After hearing Rex and Gigi talk about Nurse Wojciehowicz, who was in the hospital when abandoned baby Rex was brought in, Kyle revealed that she still worked in the hospital and introduced her to Rex and Gigi.