Susan Moore, the flirtatious cousin of Heather Webber arrives in Port Charles in 1978 and catches the eye of Mitch Williams, much to the dismay of Tracy Quartermaine. Mitch and Susan would soon begin having an affair, which continued when Mitch married Tracy in 1979. In 1980, Tracy, fed up with Susan and Mitch’s never ending rendezvous, in exchange for him breaking things off with Susan, donated two million dollars to his campaign for governor.
In 1981, Susan catches the attention of Tracy’s brother, Dr. Alan Quartermaine, who is fed up with his wife’s affair with Dr. Rick Webber. They would soon begin having an affair, not knowing that Monica is having Alan followed whenever they meet. In July 1981, Susan breaks things off with Alan. She returns shortly after and reveals that she is pregnant. Susan then relocates to New York City and secretly gives birth to her son Jason on September 14, 1981. Alan tracks her down and convinces her to come back to Port Charles. Susan gets upset by the constant pressure from Monica and Alan’s father Edward, who wants her to disappear. A furious Alan moves out of the Quartermaine mansion in October 1981 and shacks up with Susan at her cottage. After Susan kicks Alan out because he refuses to divorce Monica, he arranges for a divorce in January 1982, and they reunite.
After Alan postpones his divorce and reunites with Monica, Susan is devastated in July 1982 when Alan tells her it is over for good. Heather Webber convinces Susan to go after the Quartermaine fortune, but she has trouble finding a lawyer willing to take her case, and a distraught Susan turns to alcohol. Eventually, it is Scott Baldwin who steps in as Susan's lawyer. Susan is unaware of Heather and Scott's plans to get their hands on the Quartermaine cash. In September 1982, Susan wins a million dollar trust fund for Jason, while Susan only receives 150 thousand. Susan and Scott would become romantically involved, much to Heather's dismay. In December 1982, Susan signs a document giving Heather permission to raise Jason if anything happens to her. When a drunken Susan finds Scott with Laura Templeton, she gets into a car accident and is left in critical condition. After realizing that Heather will get everything if she dies, Susan convinces Scott to marry her on December 17. Susan has actually fallen for Scott, who is only after her money, and Alan is insanely jealous.
In January 1983, Scott uses Jason's trust fund for the renovation of the waterfront pier and builds a mall. Susan takes power of attorney away from Scott and blocks his access to what is left of Jason's trust fund; she then kicks him out of her house. Susan is later approached by Crane Tolliver, the first husband of Lila Quartermaine She wanted to blackmail them but Crane doesn't want his name to be brought up. On February 11, 1983 Crane shoots and kills Susan at her home.
In 2012, Heather revealed that Susan actually gave birth to twin boys. After Susan gave birth to Jason she started to scream in pain and she passed out. The nurse came back in with Jason and she said to Heather that Susan was still in labor with another baby so while still passed out Susan gives birth to Jason's twin brother. The nurse said that she couldn't have kids so she said maybe Susan doesn't need to know about the twins and said she should keep one of the babies so Heather sold Jason's twin brother to the nurse. The baby that was sold off grew up to be a crazy artist and serial killer named Franco, who is now reformed.
This story was later proven false in November 2013, when Heather admitted she lied about Susan giving birth to twins, to cover up the truth that she is Franco's biological mother and Scott Baldwin is his biological father. It turns out that Susan and Heather had both given birth to little boys at the same clinic in New York.