Vince Vaughn is in talks to play the central antagonist (not necessarily the villain or murderer – this is a mystery-based series after all) on the second season of HBO’s “True Detective,” while “Mad Men” star Elisabeth Moss is being eyed for the female lead and “The Killing’s” Michelle Forbes is in contention for a key role on the show, TheWrap has learned.

Colin Farrell is nearing a deal to star, while Taylor Kitsch is the frontrunner to play the younger male lead, as TheWrap first reported.

HBO had no comment on casting decisions.

According to a breakdown obtained by TheWrap, the second season of “True Detective” will follow the death of a corrupt city manager of a fictional California city who’s found brutally murdered amid a potentially groundbreaking transportation deal that would forever change freeway gridlock in the state. Three law enforcement officers from different cities and branches of the government are tasked with finding out who did it. They soon discover their investigation has much broader and darker implications than they initially thought.

Also read: Colin Farrell in Talks for ‘True Detective’ Season 2; Taylor Kitsch Also Eyed

Vaughn is in talks to play Frank Semyon, a former thug-turned-businessman who’s working with a local mayor and his political cohorts to spearhead the construction of a high-speed railway system that links Southern California to Northern California in order to reap financial gains from federal grants and land purchases.

Moss, who recently played a small-town cop in the similarly themed, “Top of the Lake,” is being eyed to play Ani Bezzerides, a tough, no-nonsense Monterey sheriff whose troubled upbringing has driven her to gambling and alcohol.

Farrell is nearing a deal to play Ray Velcoro, who has been damaged by years of turmoil in both his personal and professional lives.

Also read: 6 Questions With ‘True Detective’ Star Michelle Monaghan: Emmy Contender Quickie

Kitsch is angling for the role of Paul Woodrugh, a handsome, 28-year-old military veteran who has seen his own share of violence and destruction. Forbes, who starred on the first season of “The Killing,” has been rumored for a part on “True Detective,” and it’s possible she could play either Farrell’s ex-wife (a survivor of sexual assault) or Vaughn’s charming but mercurial wife.

TheWrap previously reported that the second season of “True Detective” would feature three leads — two men and one woman — while series creator Nic Pizzolatto has said there will be four leads. While the three investigators are clearly the leads, it’s understandable why Pizzolatto often referred to the season’s primary antagonist as a fourth lead — he was writing the role with movie star Vaughn in mind, which explains the discrepancy in semantics.

Pizzolatto is still fine-tuning the script as HBO searches for multiple directors to tackle the second season. Cary Fukunaga directed every episode of the first season, but HBO does not expect a filmmaker to commit to the entire second season, and is looking to hire several directors for multiple episodes — possibly two or three apiece.

Andrew Dominik was one of the filmmakers that HBO is rumored to have approached. But it’s believed he’s too busy prepping the Marilyn Monroe movie “Blonde,” which will star Jessica Chastain, who already passed on the female lead in “True Detective.”

Vaughn has been looking to do something darker than his typical comedic fare, and “True Detective” certainly fits that bill. He is represented by CAA and his potential casting was first reported by TV Line.

For its part, HBO has not commented on any “True Detective” speculation thus far.