Official details about Luke Grimes’ Kayce Dutton Yellowstone spinoff, Y: Marshals, suggest that John Dutton’s (Kevin Costner) youngest son has serious tribulations on the horizon regarding his relationship with Monica Long (Kelsey Asbille). While the original series ended with Yellowstone Season 5, as John Dutton’s death rippled through the series, the franchise will continue the story with several continuations set to debut next year. That includes a Kayce-focused tale, where he will join an elite team of US Marshals.

Kayce Dutton’s spinoff is taking form, with key details about its cast and potential storylines emerging. The show will be the franchise’s first show to air on a major network, with CBS set to host Y: Marshals on its spring schedule, which will also mark the Yellowstone franchise’s first procedural. That said, the continuation will certainly feel different from Yellowstone, but if anyone can pull off a shift in tone for the franchise, it’s Kayce. Still, a huge obstacle lies ahead for Dutton, which the series will need to explain.

Kelsey Asville Isn’t Joining Y: Marshals As Monica Dutton

While many would think that Monica Long Dutton, Kayce’s wife, would be a cornerstone of Dutton’s next chapter, the cast of Y: Marshals will not include Kelsey Asbille, who plays his sweetheart in Yellowstone. That comes as quite a shock to Yellowstone audiences, especially since the official description of Kayce’s show teases that Dutton “must balance family, duty and the high psychological cost that comes with serving as the last line of defense in the region’s war on violence.” Still, only part of Kayce’s family will return.

While Asbille seemingly isn’t joining its ranks, the cast of Y: Marshals will include familiar faces, with Gil Birmingham, Moses Brings Plenty, and Brecken Merrill reprising their roles as Thomas Rainwater, Mo, and Kayce and Monica’s son, Tate. Kayce and Monica discussed potentially having another child in Yellowstone Season 5, following the loss of John Dutton IV, and that was one direction the show could have taken. Instead, it appears that Kayce is separated from Monica, indicating that something has come between them.

Something Could Come Between Kayce & Monica Dutton

Sadly, Kelsey Asbille not joining the cast of Y: Marshals likely means that something has come between Kayce and Monica. The first episode of Y: Marshals will need to explain the development if the answer isn’t revealed any sooner, potentially in an official trailer that tells more about the plot. Audiences will undoubtedly need an explanation as to why Monica will no longer be by Kayce’s side after their rich history in Yellowstone. It’s unlikely that Monica is just not involved in the series, and the reason for her absence could lead to more tragedy for Kayce.

The top reasons that come to mind for Monica not joining the show are either that she and Kayce have gone their separate ways and are divorced, or that Monica Dutton is dead. Monica had a near-death experience at the beginning of Yellowstone Season 5, getting into a serious car wreck with Tate that killed her baby at the end of the premiere. While it would be a grim fate, perhaps the event was foreshadowing, and Monica won’t live to see the new series. The couple had already worked through many of the issues that had almost led to a split in the past.

What Monica’s Absence Means For Kayce & Y: Marshals

Regardless of why, Monica’s absence will have a pervasive effect on Kayce Dutton’s next chapter. His relationship with Monica was one of the main drivers of Kayce’s motivations in Yellowstone, so a chapter that doesn’t include her is likely to lead to significant character growth for Kayce. In an official promo for the series, which gave a first look at Kayce Dutton in Y: Marshals, he says that he is changing paths and looking for a new beginning, which could be a sign that Kayce is moving on from one of his most formative relationships.

Therefore, perhaps Kayce is not only embarking on a new path with a team of US Marshals, but there’s also a fresh personal journey ahead. His relationship with Monica dates back to his teenage years, so for Kayce to emerge on the other side of it in his thirties will likely lead to groundbreaking new developments for Kayce, who is already one of the most dynamic characters in Yellowstone. That will likely include conversations with his son, who is joining the series, about what the changes in their family mean for his next chapter as an adult.

With all Kayce’s losses, including his father, his infant son, and now seemingly his most formative relationship, Y: Marshals needs to delve deeply into Kayce’s new reality and how he’s processing all the changes that have happened in Yellowstone‘s final season and beyond. Looking forward, new characters will fill out Y: Marshals, including two female marshals, which could potentially mean a fresh romance for Kayce. Regardless, perhaps it’s the last we’ve seen of Monica Dutton in Yellowstone, which is genuinely the end of an era.