The Gilded Age Season 3 Episode 4 finally brings to the forefront a character mentioned in the show’s opening episode. At last, Bertha Russell (played by Carrie Coon) finds herself obliged to welcome her sister, Monica O’Brien (portrayed by Merritt Wever), to 61st Street. Die-hard Gilded Age enthusiasts may remember that George Russell (Morgan Spector) proposed inviting Monica to their grand home as soon as they moved in, but Bertha dismissed the idea. Her focus was on forging connections with the elite society of “old” New York. Now, however, she must yield to family pressure and invite Monica so she can be part of Gladys’s (Taissa Farmiga) extravagant wedding to the Duke of Buckingham (Ben Lamb).

Though we’ve just been introduced to Monica in this episode, she already feels like a well-developed character and a cherished addition to the Russell family. This is significantly due to the performance of Emmy-winner Merritt Wever. Her seemingly effortless integration into The Gilded Age stirred a bit of envy in Carrie Coon.

“Naturally, Merritt not only fit in flawlessly, but she also made me feel inadequate because she’s such a genuine and effortless actor,” Carrie Coon shared with DECIDER. “Watching someone like Merritt Wever step onto our set and immediately exude authenticity — something we struggled to achieve in the initial stages — just made me think, ‘I’m doing it wrong!’ That was my experience.”

After laughing about this, Coon explained that one of the best parts about welcoming “marvelous actors” like Merritt Wever onto the show is how the rest of the cast is “always learning” from them.

“Merritt describes, she said, ‘The channel is so narrow that you have to walk in the show because you can feel too theatrical, but you could also feel like you’re too small for the costume and the space,’” Coon said. “And I thought that was a really good description. Like you just have to find that ‘channel.’”

Merritt Wever has a long career of figuring out exactly how to calibrate her talents for a variety of genres on TV. After winning the Emmy for her comic work in Nurse Jackie, she went on to deliver stunning performances in the Western Godless, the crime drama Unbelievable, dark rom-com Run, and the Apple TV+ hit Severance.

Morgan Spector revealed to DECIDER that his favorite part of working with Wever on The Gilded Age was finding a shared inside joke between George Russell and his sister-in-law.

“I also enjoyed how, you know, George and Monica only have like a couple of little moments together, but I feel like the history that I felt that we both got to bring that moment was like a history of kind of looking at Bertha and being, ‘Jesus Christ.‘” he said, raising his eyebrows.

“‘There she goes again,’” Coon echoed, with a giggle.

“Which was really, really fun to play with Merritt,” Spector said.

In addition to welcoming Merritt Wever as Bertha’s sister Monica, The Gilded Age Season 3 Episode 4 also introduced the Duke’s sister, Lady Sarah (Hattie Morahan), and Andrea Martin as a psychic whom a grieving Ada (Cynthia Nixon) visits in an attempt to reach her dead husband Luke (Robert Sean Leonard).

“So we loved having her,” Coon said, “as well as all the other marvelous Broadway actors we got to add to our company this year.”

“It’s just…it’s an embarrassment of riches, truly.”