Lauren Cohan, Mark O'Brien and Mia Tomlinson Join Amazon's 'Stillwater'

Lauren Cohan, Mark O'Brien and Mia Tomlinson have joined the cast of "Stillwater," Amazon Prime Video's eight-episode adaptation of the graphic novel by Chip Zdarsky and Ramón K. Pérez. The three join previously announced lead Ben Hardy in a series Warner Bros. Television is producing with Berlanti Productions, Skybound Entertainment and Amazon MGM Studios.

Cohan, best known as Maggie Greene in "The Walking Dead," will play Catherine "Cat" Keegan. The character is a former homecoming queen whose small-town charm has sharpened into something fiercer through decades of grudges and regrets. Cat is deeply loyal to her husband Ted, a sheriff's deputy, and has spent years convincing herself that the things they do to protect the town's secret are justified. It's a familiar register for Cohan — loyal, hardened, morally cornered — with fewer zombies.

Who are the Keegans?

O'Brien takes on Ted Keegan, a father, farmer and military veteran. The official description calls him a "hardened man who's spent much of his life following orders and keeping secrets. As a deputy in Stillwater, he enforces the town's strict policies, sometimes through violent means, all while hiding a truth that could destroy his own family." His credits include "Nuremberg," "Marriage Story," "Arrival," "Ready or Not" and the TV show "The Copenhagen Test."

Tomlinson rounds out the family as Laura Quinn, Cat's younger sister — a spirited single mother with a stubborn streak and her hands full. Per the casting description, "When her hometown changed overnight, Laura faced an impossible choice that would alter her future — and the town as a whole — forever." Tomlinson most recently starred in "The Conjuring: Last Rites."

What is Stillwater about?

The series is officially described as "a mind-bending horror thriller that focuses on ex-con Daniel West." The premise, per the release: "When Daniel receives a mysterious letter promising answers about his past and a substantial inheritance in the small town of Stillwater, he discovers a community where nothing ever ages, no one ever dies, and nobody ever gets out."

Ben Hardy stars as Daniel. Series writers and executive producers Greg Berlanti and Carly Wray said in a statement: "We've been fans of Ben's for a long time, and we're thrilled to get to tell this story together. There's a toughness to him, but also something incredibly open and soulful underneath it. Daniel needs both. From the moment we saw Ben in the role, it was impossible to imagine anyone else."

Who's making it?

The executive producer roster runs long:

• Greg Berlanti and Carly Wray (writers and EPs)
• Sarah Schechter, Leigh London Redman and Robbie Rogers via Berlanti Productions, under its overall deal with WBTV
• Robert Kirkman, David Alpert, Rick Jacobs, Glenn Geller and Chip Zdarsky via Skybound Entertainment
• Jonathan Gabay

Kirkman's involvement carries weight here. The "Walking Dead" creator's Skybound adapted Zdarsky's comic once already — a pedigree that suggests Amazon is betting on proven horror-brand machinery rather than an untested property.

Cohan is represented by Anonymous Content, CAA and Hansen Jacobson Teller. O'Brien is represented by UTA, Thruline Entertainment, Lichter Grossman Nichols Feldman Rogal Shikora & Clark, and The Characters Talent Agency. Tomlinson is represented by UTA, Julian Belfrage Associates and Peikoff Mahan.

Amazon has not announced a premiere date. With the core family cast now set, expect the eight-episode production to move toward cameras — and expect the town of Stillwater to keep its secrets a while longer.