Leta Aider appears in three episodes of Quantum Leap titled "Trilogy Part I: One Little Heart", "Trilogy Part II: For Your Love", and "Trilogy Part III: The Last Door". The part of Leta is played in the episodes by Mary Gordon Murray.
About Leta[]
When Sam, as Sheriff Clayton Fuller in 1955 Louisiana, a widower with a 10-year-old daughter, Abigail, finds his deputy, Deputy Sheriff Bart Aider, dead in a nearby swamp, Leta, who is unstable, blames Abigail for his death, and that of her daughter Violet, who disappeared from their home in 1953, this after Abigail had been the last person to see their daughter Violet before she disappeared and presumably died two years before.
Sam, in his leap mission, is to save young Abigail from the raging wrath of Leta, who winds up cornering her in the Fuller house, demanding that she confess to the crimes of murder of her husband and daughter; in the original timeline of events, both Abigail died in a house fire after Leta set it ablaze with her in it on the night of August 8, 1955.
Sam, as Clayton, visits the mental hospital where wife Laura Fuller is hospitalized in hopes of trying to get more information about Leta, who had, two years earlier in a heated argument with her, insulted her and called her crazy, saying that she should be committed and "not allowed to have anymore crazy children". Al, with Ziggy's help, warns him that Leta is at the Fuller home, tormenting and threating Abigail, trying to get a murder confession out of her, as she then sets the home ablaze, it's now the sheriff's, or Sam's, mission to save and rescue Abigail from the house by breaking a bedroom window and getting her to jump out of it, as he is able to do so, confronting Leta, who is able to sneak out of a backroom door as the fire blazes before he, or the Sheriff, dies in the blaze as a fiery wooden beam collapses and falls down from the ceiling, as Sam leaps.
Leta corners young Abigail Fuller, in trying to get her to confess to the murders of her husband and daughter in Part 1 of the "Trilogy" story arc in Season 5 (ep.#8).
Fast forward to 11 years later, in 1966, when Abigail is set to marry Will Kinman, now the Deputy Sheriff, it's Leta, who presses to have Abigail tried for the deaths of her family, and of a young boy who was entrusted to Abagail's care, as Sam, as Will, is again used to rescue her from the wrath of the townspeople, as they almost lynch Abigail.
Again, 12 years later, in 1978, Sam, this time as a Lawrence "Larry" Stratton III, a now retiring attorney who was there in 1966 when Abigail was originally lynched over the charge of the death of the young boy she babysat for. Fortunately for Abagail, her now 10-year-old daughter Sammy Jo, happened to be hiding behind the kitchen door, as she witnessed a disturbed, raging Leta practically destroy Abigail's kitchen, and in deep scathing hatred for her mother, rants over the murders of her family she takes a kitchen knife, and kills herself, clearing Abigail of any charges.