Teenager Karen Haines was introduced when her mother, Cynthia, fell for and became engaged to a man named Donald Saunders. Donald suffered from amnesia and had no idea who he was. Deeply in love with Donald, Cynthia’s world was shattered on her wedding day when a young woman recognized Donald as her father, David Stewart! With that revelation, the wedding was put on hold and David, who had a wife, returned to Oakdale where his memory soon returned. Though Cynthia’s heart was broken when David ultimately chose his wife over her, she allowed Karen to go to Oakdale to attend college. David treated Karen as another daughter, much to the consternation of Dee Stewart and her older sister, medical student, Annie Stewart.
On her first day in Oakdale, Karen was looking for work and not having much success. She stopped in front of a store that seemed to be already closed, Fashions, Ltd., The door was open, but nobody seemed to answer when she called out. Karen then found a young man, passed out. Karen immediately called for help and him got to Memorial's ER in the nick of time where the angel dust was gotten out of his system. The man, Eric Hollister, though did end up in a coma for several weeks. During this time Karen celebrated her 18th birthday, but instead of a huge celebration, Karen opted to be a nurse to Eric during the time he was unconscious. When Eric finally, awoke, everyone erroneously assumed that he was a drug addict because of his overdose. The only person who stood by Eric through all of this was Karen. Eric found comfort in Karen’s willing arms and they temporarily became lovers and moved in together. However, when Karen started to realize that Eric's heart belonged to Hayley, she released him from any obligations and told him their love affair was over.
Later, Karen found herself charmed by Dr. Jeff Ward. Though Jeff did date Karen, his heart belonged to his best friend, Annie Stewart. Though Jeff began dating Annie, he gave in to the seductive Karen. Eventually, Jeff told Annie how much he loved her, but Annie wasn't sure of her feelings and Jeff turned back to Karen. In the spring of 1982, Annie passed her medical exams and began her residency at Memorial, and Jeff arranged for her to work with him. Annie finally told Jeff she loved him. When Jeff told Karen, she became hysterical and was admitted to the hospital with no memory of their conversation. Jeff and Annie tried to talk to her, but Karen freaked out and attacked Annie. David was angry at Jeff for leading Karen on, and Annie was upset by her father's devotion to Cynthia's daughter. When Jeff sent Annie a note about a date, Karen intercepted it and changed the time. Later, she snuck out and went to Jeff's apartment. Annie arrived and found Karen in a towel. Jeff couldn't understand why Annie was mad at him. Annie finally figured out that Karen was trying to come between them and set a trap. Karen found a love note from Jeff to Annie and the message read, "You're caught." In the meantime, Annie, who had suffered a few miscarriages, was devastated when a fertility test stated that she was unable to bear children. Though Annie did end up pregnant, her joy was tempered by the fear of losing the baby. Suspicious, David wondered about Annie's test, and when he rechecked, he realized someone had tampered with it. He told Cynthia that he suspected it was Karen. Cynthia advised her daughter to tell the truth or leave town. Soon after, Karen finally admitted responsibility.
Meanwhile, Karen accidentally discovered a tape that revealed that James Stenbeck wasn't the true Stenbeck heir. Not long after, the greedy Karen blackmailed James into marrying her, threatening to reveal his true heritage if he didn't. James promised Karen a married life of hell and had her sleeping in the maid's quarters. Soon, Karen got caught up in the intrigue between James, his ex-wife, Barbara, their son Paul, and Barbara’s lover, Gunnar St. Clair. In the meantime, Karen, was aroused when she saw how much time Ariel Aldrin was spending with the new horse trainer, Burke Donovan. Ariel claimed that she and Burke had once been lovers, but now were just friends. Karen didn't buy this and asked Burke, who replied that he'd known Ariel for only three weeks! Later, the persistent Karen got the name of Burke's late wife's parents and told that James she was going on a trip. When she met with them and brought up Gunnar's name, it was obvious that, because of their affair, they blamed Gunnar for their daughter's death. On the plane home, Karen realized that Ariel was after Burke because she'd figured out that his teenage son, Dusty, could be the true Stenbeck heir. In the meantime, Karen tried to make friends with Paul, but James said it wouldn't be necessary, since Paul was going to Europe. Karen divulged this to Barbara who took steps to keep James away from their son. Though Karen did try to goad James into fighting for custody of Paul, to ensure that he’d keep his fortune, when she learned that James kidnapped Paul from camp, she sided with Barbara and Gunnar and left James for good. With nowhere to go, Karen took John Dixon up on his offer of an extra bedroom.
In the meantime, Karen’s friendship with Burke and Dusty Donovan was growing, as was Burke’s feelings for Ariel. . Unfortunately, Dusty saw Ariel as a manipulator and confided in Karen that he didn't want his father marrying her. Not liking Ariel herself, Karen told Dusty to tell his father what he thought. Dusty did and, as a result, Burke stopped the nuptials. At the same time, Karen learned that Burke was dying of Wilhelm’s disease. Knowing how close Dusty and Karen had gotten, Burke arranged for Karen to get custody of Dusty after his death. Since the courts were wary of giving custody to a single woman, Karen married John. Unfortunately, their married life was not easy. When Karen learned that John was the one who suggested that Marcy Thompson wrongly file sexual harassment charges against Bob Hughes, Karen was so livid that she insisted on separate bedrooms. By the time she allowed him back into her bed, John was fascinated by Lucinda Walsh and her riches. Soon, Lucinda started taunting Karen that she wasn't a good enough wife for a doctor such as John Dixon. John also began listening to Lucinda's low opinion of Karen. It didn’t take Karen long to realize that John was drifting from her and she decided to leave town, leaving Dusty in John’s capable hands.