A new frontier awaits Lost alum Matthew Fox.

The actor has joined the cast of the Yellowstone spinoff The Madison as a character named Paul, described simply as a self-reliant bachelor who loves the outdoors. Fox joins previously announced stars Michelle Pfeiffer, Patrick J. Adams, Elle Chapman, Beau Garrett, and Amiah Miller. 

The first spinoff to be set in present day, The Madison — previously titled 2024 — will follow a New York City family in the Madison River valley of central Montana and serve as a “heartfelt study of grief and human connection,” per the logline.

Pfeiffer, who also executive produces, leads the series as matriarch Stacy Clyburn. Adams will play Russell McIntosh, an investment banker who “has followed the life path set before him from the start,” while Chapman will portray his wife Paige, described as a “somewhat self-centered woman who indulges in a luxurious New York lifestyle provided by her parents and husband.”

Garrett will play Abigail Reese, a “resilient and sardonic New Yorker” and recently-divorced mother of two, while Miller will play her eldest daughter Bridgette.

Taylor Sheridan will executive produce alongside Pfeiffer, David C. Glasser, John Linson, Art Linson, Ron Burkle, Bob Yari, David Hutkin, Christina Voros, Michael Friedman, and Keith Cox. The Madison is the third spinoff from Sheridan’s Yellowstone universe, following 1883 and 1923.

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Fox is best known for his Emmy- and Golden Globe-nominated role as Jack Shephard in the survivalist series Lost and as Charlie Salinger in the 1990s series Party of Five. Most recently, he starred in the comedy series C*A*U*G*H*T and miniseries Last Light. Upcoming projects also include the Max drama series The Assassin, based on the book series by British novelist Tom Wood.

As for the ever-expansive Yellowstone Cinematic Universe, Matthew McConaughey was previously rumored to be involved in a spinoff. Other spinoffs in development include 6666 and 1944. The flagship Yellowstone returns for the second half of its fifth and final season on Nov. 10 sans lead star Kevin Costner, who confirmed in June that he would not return for the final episodes.

“I wanted to work more than once a year and it was important that I made room for Yellowstone and made room for Horizon, but people ran through deadlines,” he told CBS Mornings of balancing the series with his film franchise. “They were busy; they had a lot to do . . . Yellowstone was my first priority, but at a certain point when you make commitments you just have to live with them.” 

But that doesn’t necessarily mean he’s saying goodbye to John Dutton for good. “I’ve never missed any obligations in my entire career, so the idea [of returning] is wide open for me,” Costner added. “It just happens to be, can I fall in love with the writing? Can I fall in love with the part to go forward?”