Donna Eleese Beckett was a scientist at Project Quantum Leap and the wife of Dr. Samuel Beckett. Due to Sam's partial amnesia and the Top Secret classification of any information regarding her, very little is known of Dr. Eleese beyond the fact that she met Sam while they were both working on Project Star Bright in the 1980s. The couple was briefly reunited during the season 4 episode The Leap Back. On the Quantum Leap TV series, Donna is played by Teri Hatcher in the Season 1 episode "Star-Crossed" and then by Mimi Kuzyk in the Season 4 premiere episode "The Leap Back".
Sam and Donna may not have been married in the original timeline; intimacy issues caused by Donna's relationship with her estranged father ultimately caused her to abandon Sam at the altar during their attempted wedding. Sam's third leap provided an opportunity to change this, with Sam leaping into one of Donna's college professors. He was able to help her patch things up with her dad, potentially changing history and allowing them to marry as planned (Star-Crossed).
A Young Donna Eleese (played by Teri Hatcher) in the episode "Star-Crossed" in Season 1.
It is also possible that there was a second, successful attempt in the original timeline, which Sam did not initially recall due to his amnesia. Neither theory was officially endorsed in the show; the former is supported by novels, however the latter would explain why Sam recalled being married when he regained his memory during "The Leap Back."
Relationship progression[]
In the episode Star-Crossed, Sam ran into Donna when she was still just a college student, before they met in the regular timeline. Of course, Sam was not Sam here; he had leaped into a professor of Donna's. He tried to convince Donna that he was not who he appeared to be by having her look into his eyes. Donna did seem to notice something, but got uncomfortable and walked away from Sam.
Later, Sam (still as the professor) talked to Donna about his theories of a finite universe, upon which his string theory (for time travel) was based. When Sam remembered that her father had left her as a child, he arranged for a reunion for them, hoping that fixing this broken relationship would keep her from running away from men as an adult. But Al reminds Sam that she had left one other man at the altar before Sam, and that if the rift between Donna and her father were fixed, she would most likely end up marrying the other guy instead.
However, in the episode The Leap Back, the audience learns that Donna did marry Sam in the changed history. She had told Al not to inform Sam of their marriage, because she didn't think he could fulfill his missions properly (which sometimes involved romancing women) if he knew he had a wife. Sam finally remembered Donna when he switched places with Al and came back to the year 1999. Donna told Sam that she never felt betrayed by any of his actions with other women.
Unfortunately, Sam needed to leap back in Al's place in order to save Al's life. Donna was initially upset and didn't want Sam to leave again, but she eventually realized that Sam was right. She herself was the one to push the button on Ziggy's console to send Sam back in time again. Upon learning that Sam had once again gotten amnesia from the leap, Donna strictly forbade Al from reminding Sam of the marriage, so Sam could continue to fulfill his missions. Donna believed that Sam would come back to her again one day. (As of Mirror Image, this has yet to occur.)
Al does seem to try to drop hints to Sam about Donna. In The Americanization of Machiko, Sam sweats before the wedding of the guy he's leaped into, and Al comments, "Funny. You didn't sweat the first time." Sam: "I'm MARRIED?" Al: "Uh, just kidding!" Al also reminds Sam of their simo-leap in Permanent Wave and Lee Harvey Oswald, Part I.
Non-canon appearances[]
Donna made appearances in several of the novels. In Knights of the Morningstar, Donna wrote a letter to Sam's mother explaining how difficult it was to live without Sam sometimes, though she eventually tore that letter up and wrote a much simpler note instead. The reader also learns that before Sam left again, he gave Al a note with some money so that Donna could get a birthday present every year from Sam, even if somewhat indirectly.
In Random Measures, Al recalls Sam's wedding day, and how he initially pretended to forget the wedding rings as a joke, then realized that he actually had lost them. Sam was furious, but Donna thought it was hilarious. Al also remembers how shocked he was the first time he came back into the Waiting Room and discovered Donna there, as a result of the changed history. He also muses to himself that sometimes Donna won't be there because of a change Sam makes, and then when Sam changes something else, she'll suddenly be back.
In Independence, Sam falls for one of his own ancestors from the Civil War, not realizing that his attraction to her is based on how similar she happens to look to Donna.
In Mirror's Edge, a story that takes place just before "Mirror Image," Donna enters the Imaging Chamber with Al to tell Sam that their marriage was probably a mistake, which would explain why Sam doesn't think about returning to her in the subsequent story. However, as with all the novels, no elements are canon unless established by a future movie or TV show.