Kate was introduced with her son Lucas. She was the whiz kid brought into to head Titan Publishing. A relationship with Victor soon came to be. He asked her to marry him. Lucas pursued the identity of his father, much to her dismay. Laura constantly confronted Kate about her affair with her then husband, and even threatened to tell. Billie was put on trial for Curtis Reed's murder. It was revealed that both Billie and Austin were Kate's long lost children. Lucas became embittered, and Billie HATED her mother because she had taken Countess Wilhemina away from her. Austin wasn't so hard on his mother.
Kate, to ensure her place in the Kiriakis legacy, wanted to give Victor another son. He was estranged from Bo at the time. Some embryos were formed, and through some shrewd trickery, Vivian had them implanted in her. She gave birth to Philip, and while pregnant, drove quite the wedge between Kate and Victor, who was supposedly married to Kate. Not to be, because Victor was married to Vivian, who had tricked him. Vivian then sent Kate on a plane and sabotaged it, causing it to crash somewhere over the ocean.
Kate was assumed dead, leaving Victor with a new son and no wife. Kate arrived back about a year later, and Vivian wasn't very happy. She was finally breaking into Victor's heart. Vivian was kicked out of the Kiriakis mansion after her machinations came to light. Kate got involved with Titan again. Soon after, Billie returned from Paris. Franco Kelly came to town also. Victor had a heart attack and was placed in a nursing home. Kate had hired Franco to break up Bo and Hope, so Billie could be happy with Bo. Sami started blackmailing Kate with her past as a prostitute.
Franco was murdered by Lucas and Kate framed Sami. Kate also knew Franco was involved with the mob, and held it over his head. He courted Sami to get a green card, and Kate knew it, but didn't let Franco marry Sami. So right now, Kate is trying to keep her family together without going to jail for conspiracy to murder. Sami was convicted and sentenced to death, Kate said that Roberto confessed to Franco's murder and Sami was freed at the last minute. Kate is now still trying to keep the secret of Franco's murder and battle with Vivian over control of Titan. Kate is also on the brink of an affair with the much younger Nicholas Alamain.
Kate and Nicholas had a torrid affair, but he left town, and she attempted to get Victor to marry her once again. She blew her chances, though, when she was caught in flagrante delicto with mob boss Vincent Moroni. She conspired with him to kill Victor at the coronation, and her plan set a horrible gun play in motion that killed Vincent's only child, Angela, and prompted Vincent's suicide. Victor realized her plan, and escaped with his life (after faking his death). He revealed himself to her the night she set the house on fire and attempted to murder him with a poker. Luckily, Victor got out, but Lucas wasn't so lucky...he was in the house that night, drunk, and ended up with severe burns.
Victor exposed Kate and kicked her out on her ear, forcing her to find work at a diner. Out of respect for their son, Victor didn't tell Philip that Kate had attempted numerous murders and was the reason that Lucas nearly died. Thanks to Philip's pleas, Victor finally agreed to provide Kate with a small allowance. She got a job at Basic Black, and began dating Roman Brady, terrified that at any moment, her secret could come out and destroy their relationship. Kate became one of the top suspects in Abe's murder because he knew her secret, but Kate finally broke down and confessed to Roman, which ended their relationship. When Lucas overheard Sami and Kate talking about Kate's past and the fact that Lucas's father's identity was unknown, he turned his back on her.
Kate and Roman were able to work their way back to each other because their love was just too strong to deny. Roman asked Kate to marry him, and she happily accepted. They had a beautiful wedding, with all of their friends and family in attendance, but Kate was shattered when, at the wedding reception, she found Roman's dead body. She mourned him deeply, but that didn't stop her from doing her best to destroy her son Lucas' newfound relationship with Roman's daughter Sami, who she swore she would try to get along with. She threw herself into her work (and destroying Sami), and the closer Sami and Lucas got, the more convinced Kate was that her only hope for happiness lay with Philip, and she began 'encouraging' him to spend more time with Belle. When Lucas and Sami got engaged, it took everything Kate had not to lose it.
Kate also moved on in her personal life, becoming engaged to John Black after months of helping him deal with a drug addiction. But just as the two were planning their lives together, their presumed dead spouses returned to Salem. Roman soon washed his hands of her, and she didn't help her situation by exposing Sami as Stan on her wedding day -- even Lucas turned his back on her. Alone again, Kate invited John Black to move in with her after Marlena kicked him out of the penthouse in favor of her returned-from-the-dead husband Alex North, but her attention was soon snapped up by a different matter -- Kate realized that there was no way Philip could by baby Claire's father and that the father had to be Shawn, and was determined to keep everyone from finding that out.
Kate tried to comfort Philip when the truth came out, but he left town. She was terrified when he went missing, but relieved when, despite needing extensive surgery, he came back determined to get his daughter and his wife back. His overtures to Belle were unsuccessful, but the courts granted him temporary custody of Claire while ordering Belle and Shawn to get their lives together. Kate was devastated for Philip when Shawn and Belle grabbed Claire and fled, and was determined to help him get her back, although uncomfortable with the growing level of violence Philip became exhibiting.
With Phillip chasing after Belle and Shawn, Kate turned her attention back towards Lucas and Sami. First, she enlisted the help of her current boardroom and bedroom partner, E.J. Wells, to seduce Sami away from Lucas. But, his efforts failed when E.J. Wells was revealed to be E.J. DiMera, the long lost son of Susan Banks and Stefano DiMera. Desperate to break them up, Kate slipped a photograph in the slide show that was shown at the reception. The photo showed E.J. and Sami together the night that E.J. fled town. But, that didn't stop Lucas either. He and Sami started their life together, despite Kate's interference. In retaliation, Lucas turned Kate and E.J. into the FTC for their questionable financial records. Kate was broke.
Kate turned to Stefano for money. In exchange for sleeping with him, Stefano gave Kate enough money to start her own business. Kate started "Kate's Hearth and Home", a Martha Stewart-like brand of housewares. She hired Tony DiMera to do her advertising and her business became very successful.
Kate didn't have to worry about Lucas and Sami much longer because Sami soon divorced Lucas to marry E.J., as part of an agreement with Stefano that would end the Brady/DiMera feud. That meant that Kate could turn her attention back to Phillip, who was involved in a bitter turf war with John Black DiMera, and Chelsea, who was recovering from major surgery.
Chelsea's recovery went well and she soon started dating her surgeon, Daniel Jonas. However, after they started dating, viewers learned that Kate had a brief and passionate affair with Daniel. Kate begged Daniel not to ever let Chelsea find out.
Philip became a suspect in the disappearance of Paul Hollingsworth, a corrupt customs official who had been working both sides of the DiMera/Kiriakis turf war, and Kate was adamant about keeping Philip safe. When Victor told Kate that a tape recording had surfaced that could incriminate Philip, Kate took the tape from Victor and burned it.
Philip was subsequently cleared of all charges. Meanwhile, Chelsea and Daniel continued their relationship. But, Chelsea found a text message from Kate to Daniel. Kate's secret was out. Chelsea broke up with Daniel and was furious with Kate. Kate tried to apologize, but Chelsea could not forgive her and left town in distress. While Chelsea was gone, Kate resumed a relationship with Daniel.
In November 2008, Daniel diagnosed Kate with stage 4 lung cancer and recommended an immediate and aggressive treatment plan- a bone marrow transplant. A hospital-wide search came up with Chloe Lane as a match. Chloe donated her bone marrow to Kate. As Kate began her recovery, she couldn't help but notice tension between Chloe and Daniel.
A few weeks later, she saw Kate and Daniel kissing in the park. Furious with Chloe for cheating on Lucas, Kate set a plan into motion to get revenge on Chloe. Kate poisoned brownies that Chloe ate and Chloe fell into a coma. Kate planted the bottle of poison in Daniel's apartment. She also doctored a recording of Daniel and Chloe's voices to make it sound as though they were having an argument and played the recording over the phone to Maggie so Maggie would testify that Daniel was threatening Chloe. Despite his adamant testimony that he loved Chloe and would never hurt her, the police arrested Daniel.
But Daniel did not give up on Chloe or a confession from Kate. He goaded Kate into confession to the crime by promising to start up their relationship again. But he taped her confession and promised to use it against her. Kate knocked Daniel unconscious and left him tied to a bed in a hotel room. He managed to escape. Frightened that Daniel would be able to incriminate her, Kate struck a deal with Stefano. He made sure that she didn't go to jail for crimes against Daniel and Chloe. In return, Kate married Stefano. They married at Chez Rouge on September 24, 2009.
Kate and Stefano's blackmail marriage soon turned to real love. When Stefano fell ill with diabetes, Kate took charge and nursed him back to health. The two began pooling their resources to scam their enemies.
Kate found professional happiness too when she relaunched Countess Wilhemina Cosmetics. Kate' main rival was the recent Titan acquisition, Mad World Cosmetics, run by Madison James. Kate and Madison were bitter rivals. Kate plotted to take Madison down by hiring Sami away from Mad World and getting Sami to reveal Mad World secrets.
Little did Kate know that Sami double crossed Kate and kept in touch with Madison the whole time, feeding Madison Countess W secrets. However, Madison soon realized that the situation was dangerous for Sami and ordered Sami to quit. When Sami refused and quit Mad World instead, Sami committed all of her attention towards making Countess W great.
Kate's personal happiness was compromised when an old flame, Ian McAllister, came to Salem. Ian also happened to be Madison James's husband. He told Kate all about Madison and Sami's plan. Kate toyed with Sami for a while and then fired her. Kate warned Sami that the police would be notified, sometime, but didn't tell Sami when.
Then, Ian tried to convince Kate to rekindle their relationship. Kate resisted at first. But, when Kate believed that Stefano was falling for Marlena again, Kate slept with Ian. She regretted it immediately and told Ian to leave her alone. But, he insisted that they be together.
Meanwhile, Stefano was testing Kate the whole time. He was never after Marlena, but set Kate up to think that he had been following Marlena again. When Kate failed the test, Stefano vowed revenge on Kate and Ian. When he returned from his trip, Stefano used his controlling share in Countess Wilhemina Cosmetics to remove Kate as CEO and give the job to Sami. He also removed Kate and Lucas as heads of Hearth and Home. Finally, he kicked Kate out of the mansion.
Kate was heartbroken and furious with Stefano for testing her. But, Kate wasn't the only one furious with Stefano. One night everyone that Stefano had hurt in the last few months -- E.J., Will, John, Marlena, Kate, Bo, Hope, and Abe -- confronted Stefano with a gun. Stefano was shot and assumed dead.
But, it was actually Ian McAlister who shot "Stefano." (Ian found a double for Stefano and that's who was shot and killed at the mansion. And, Ian had been keeping a very much alive Stefano and framing E.J. for the murder. Eventually, E.J. discovered that Stefano was still alive. While Stefano was eager to make amends with E.J., Stefano had no interest in reconciling with Kate. Stefano sent Kristen to give divorce papers to Kate. After one final attempt to reason with Stefano, Kate reluctantly signed the papers on November 27, 2012.
Kate was still reeling from the loss of her marriage when she drank a little too much one night and ran into an also-intoxicated Rafe. The two ended up in bed together, despite being on different sides of a potential paternity battle -- she on Team Will and he on Team Gabi. But, the two decided that the real problem was Nick, so they decided to have a talk with him.