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Catherine is first introduced in Summer Kind of Wonderful as the mysterious married woman that Nate Archibald has been having an affair with. While at The White Party, Nate tries to make her jealous by kissing Serena, which works.
At Blair Waldorf's party in Never Been Marcused, Chuck Bass invites Catherine, knowing Blair will embarrass herself in front of her boyfriend Marcus' stepmother. She does, and Catherine informs Blair that she will never be good enough for Marcus. However, Blair is able to blackmail Catherine into feigning her approval after she catches her hooking up with Nate. As a result of his father leaving town, Catherine offers to pay Nate to sleep with her, and he takes the deal to save his family.
When Catherine finds out Nate is interested in Vanessa Abrams, she corners her and says that if Nate ever leaves her, she'll reveal where Nate's dad is hiding out from the FBI (The Dark Night). As a thanks for respecting their agreement, Catherine writes her a check, which Vanessa returns in The Ex-Files. When she tries to do so, she discovers Catherine is hooking up with Marcus. She tells Blair, who blackmails both Catherine and Marcus into keeping quiet about where Howard Archibald is, as well as paying off the Archibald debt. Vanessa wrongfully assumes that Blair isn't going to do anything and informs Catherine's husband. He then sends both her and Marcus back to London.
In Chuck In Real Life, Vanessa threatens to expose Catherine and Marcus' affair to blackmail Blair, but Blair is able to delete the evidence before she can.
- She's in a book club with Serena.