Myrtle Lum arrived in Pine Valley in 1976 after being hired by Phoebe Tyler to break up the relationship between Phoebe's son, Linc, and his girlfriend and Kitty. Myrtle impersonated Kitty's mom, Lucy Carpenter, who was actually deceased. Myrtle grew to love Kitty and rather than continuing the charade, Myrtle hired her friend, Nigel Fargate, to pose as a doctor and say that she had died. That way, Myrtle could end the scam and move back to Minneapolis and marry her good friend and love, Nigel. After Kitty's death in 1978, Myrtle returned to Pine Valley.

In the early 1990s, Myrtle and her best friend, Mona, decided to invest their money in a retirement home at Willow Lake, but thanks to Brooke and Edmund, they discovered that it was all a scam. Myrtle took Erica under her wing, and acted as a surrogate mother to Erica to help Erica through painful moments in her life.

At the end of 1996, Myrtle found herself trying to convince Red Kilgren that he was not Santa Claus. A strange sequence of events made Myrtle realize that Red might just be the jolly old elf. She helped reunite Red with his wife and subsequently saved Christmas.

In 1999, Myrtle's carnie past was revisited. While Rae Cummings was in Pine Valley searching for a daughter that had been stolen from her shortly after birth, Myrtle was forced to confront a part of her past that she'd kept secret: Myrtle had a child of her own. Myrtle went to great lengths to hide the truth about this child she'd given up for adoption - including trying to steal the adoption records from a courthouse. In the end, Myrtle realized that her daughter had come back into her life. Her daughter, it turned out, was Rae. Rae was initially furious with Myrtle for giving her up, but that anger subsided and she and Myrtle formed a very close bond.