1979
Heather worked to get her son back from his adopted mother Diana Taylor by driving Diana insane. In a plot to convince the doctors that Diana should be committed to a mental institution, Heather drugged Diana's drink with LSD but accidentally imbibed the drug herself resulting in her commitment to the Forest Hills sanitarium. After the death of Peter Taylor, Diana learned the P.J. was actually Steven Lars.

1980
Robin Mattson took over the role. Heather regained her sanity in the mental institution but faked catatonia fearing criminal charges for attempting to poison Diana. Impersonating a nurse at Forest Hills, Heather escaped the institution and overheard Jeff, who was dating Diana and falling for virginal nurse Annie Logan, say that he planned to ask her for a divorce once she recovered.

1981
Heather was released from the mental hospital and pretended to have no memory of her devious past. She arrived at Diana's apartment planning to kill her in order to keep the secret of P.J.'s identity but was startled to find Jeff and Diana making love. Heather returned to Forest Hills to plan Diana's murder. Meanwhile, Diana revealed to Jeff that P.J. was really Steven Lars, his son. After a confrontation with Heather, Diana was killed and Anne was framed for the crime. As Heather prepared to leave the institution, Jeff took P.J. and left town hoping to keep him safe from Heather. Private investigator Joe Kelly suspected Heather of committing Diana's murder, but fell in love with her during his investigation. In a letter, Jeff asked Heather for a divorce. It was revealed that Heather's mother Alice had killed Diana to protect her daughter.

1982
Heather's plans to marry Joe Kelly were destroyed when Joe learned that Heather was bedding Scotty Baldwin. Heather and Scotty competed to snag Heather's cousin Susan Moore's millions. Heather lost when Scotty married Susan and gained custody of Jason, Susan and Alan Quartermaine's son.

1983
Heather continued her affair with Scotty Baldwin and became a prime suspect when his wife — and her cousin — Susan was murdered (the killer was eventually revealed to be Crane Tolliver, Lila Quartermaine's first husband). Heather fought for custody of baby Jason — and his million-dollar trust find — with help from Alan's half-brother, Jimmy Lee Holt but lost when Monica agreed to take in her husband's illegitimate child.