|“||This place... It's like the Spine... It'll use you up.||”|
— Rebecca St. Clair to Myka, Burnout
Her original last name is unknown, and the birth year (1929) given on her obituary may be falsified. She "retired" due to her partner and boyfriend's mysterious disappearance, but continued to live in the same location in St. Louis, Missouri, hoping to find Jack one day. Like Myka Bering, Rebecca was the more "logical" of the pair, whereas Jack worked more on intuition.
In the Season 3 episode 3... 2... 1 she is seen in flashback along with Jack Secord as they investigate reports of a crashed flying saucer in Ohio in 1962, a year after Jack and Rebecca got together. They are shown to still be dating, but Rebecca expresses doubts on the effect the Warehouse has on their relationship. However, she ultimately resolves to pursue their relationship, saying that they should try to squeeze as much happiness as they could get before it ended.
After Rebecca moved from Univille to St. Louis in 1965 (when Jack disappeared on a case there), it is implied that she attended Washington University in Minnesota, and earned a Master of Arts of Education. However, it is possible that she earned this degree before she became a Warehouse Agent or Secret Service member. She then served as a teacher and administrator to Goddand-Smythe Elementary School in Kirkwood for thirty-four years. In 1988 she was awarded the Lily Guggenheim Teacher of the Year by the Missouri Commission on Elementary Teaching.
In 2009, in a similar manner that Arthur Nielsen did in the Pilot, Rebecca offered tea and cookies to the pair when they come to speak to her in St. Louis, which Peter Lattimer happily accepted. She also tipped her hand at the time regarding a "greater than public knowledge" level of the events occurring in town. Eventually, she does reveal what she knows from Jack's investigation and does help with saving Lattimer from the main artifact of the Burnout episode.
She also learned that Jack, who was planning to propose and left the ring in his desk, chose her over the Warehouse, and warned Myka to get out while she could.
In the second season, Rebecca returned in the episode, Where And When. She showed up at Leena's B&B, asking if the agents were still in the artifact finding business and explained that on August 20, 1961, she and her partner, Jack, had been tracking down an artifact that turned women to glass, but were unable to collect it. On their last day on the case, they each had blackouts, which neither could ever explain. When they awoke, all that she could remember was that Jack had kissed her in the cherry orchard they were in, which had been their first kiss and the day they'd fallen in love.
When H. G. Wells asked exactly how long they were out, Rebecca responded that they had blacked out for "twenty-two hours and nineteen minutes," leading H.G. to realize that someone used her time machine to go back, since it lasts exactly the same amount of time that Rebecca and Jack suffered the blackouts. In the crate containing the time machine, they discovered a note from Jack in Pete's handwriting and a movie made by Jack and Rebecca from 1961; it's actually Pete and Myka, whose minds were sent back to inhabit Jack and Rebecca's bodies in 1961.
Without Artie's knowledge, H.G. sent Pete and Myka back to find the artifact that is turning its victims to glass. While in Rebecca's and Jack's bodies, they make the movie to themselves and send the package to Warehouse 13 and then decide to find a place to hide the artifact, so they can get to it in the present without anyone being hurt by it in the forty plus years in between. On the way, they crash in a cherry orchard and realize that it was where they were going all along and bury the knife under the tree before passing out as they're returned to 2010.
In 2010, the time machine had become badly damaged, but Rebecca requested to be sent back to her 1961 body one last time, to see Jack again, despite H.G.'s warning that the trip would only last a few minutes and that it would be impossible to bring her back. Known only to she and Artie, Rebecca had terminal cancer (which was why she had wanted the artifact found, to fulfill her promise that she would find it before she died). With that in mind, she asked, "Why would I want to?"
Before Rebecca of 1961 woke up, Rebecca's mind of 2010 was sent to her body, and she awakened and kissed Jack, much to his surprise. As the time machine broke down in 2010, Rebecca of 1961 awoke and was surprised when Jack, who she argued with and was mean to prior, kissed her, leaving her with the memory of that being their first kiss and the day they fell in love.
Rebecca also stated in 3...2...1..., that she was afraid for her romantic relationship with Jack Secord, because "Every Warehouse agent ends up insane, or dead." Rebecca, as stated in the picture above, was a teacher. The cause of death was not stated in the newspaper article, but Artie Nielsen felt sad about Rebecca's passing.
- Given her teaching degree and response to young Daniel Farley, it is possible that she, like Jane Lattimer, had a Warehouse-esque talent for children.
- Despite having told Agents Lattimer and Bering that she changed her name upon moving to St. Louis, in 3 . . . 2 . . . 1 Agent Secord referred to her as 'Agent St. Clair'.
- Rebecca's last name, 'St. Clair', is also the name of the oldest county in Illinois, St. Clair County, which happens to lie right next to the county of St. Louis.