Texas Ranger Cordell Walker, a widower and father of two with his own moral code, returns home to Austin, TX, after being undercover for two years, only to discover there’s harder work to be done at home. As Walker attempts to reconnect with his creative and thoughtful son August and his headstrong, somewhat rebellious teenaged daughter Stella, he finds that he needs to navigate clashes with his family – Liam, Walker’s ADA brother who stepped in during Walker’s absence, his perceptive mother Abeline and his traditional rancher father Bonham. Walker’s former colleague, Larry James, is now his Ranger Captain. And Walker finds unexpected common ground with his new partner Micki Ramirez, one of the first women in Texas Rangers’ history while growing increasingly suspicious about the circumstances surrounding his wife’s death.

When nuclear Armageddon destroys civilization on Earth, the only survivors are those on the 12 international space stations in orbit at the time. Three generations later, the 4,000 survivors living on a space ark of linked stations see their resources dwindle and face draconian measures established to ensure humanity's future. Desperately looking for a solution, the ark's leaders send 100 juvenile prisoners back to the planet to test its habitability. Having always lived in space, the exiles find the planet fascinating and terrifying, but with the fate of the human race in their hands, they must forge a path into the unknown.