The official Marshals synopsis is as follows: “With the Yellowstone Ranch behind him, Kayce joins an elite unit of U.S. But one star is notably missing from the cast and trailer: Kelsey Asbille, who played Kayce’s wife and Tate’s mom, Monica. Here’s why fans fear Marshals kills off Monica and Asbille leaves the Yellowstone universe. Kayce, Monica, and Tate officially moved to East Camp and were finally settled following the Dutton family drama and John’s (Kevin Costner) tragic, unexpected death. Photo: CBSTo add to initial suspicions of Monica’s death/Asbille’s lack of involvement in the spin-off, earlier this week CBS dropped a gripping Marshals trailer, and Monica was nowhere to be found.