The Leftovers is adding to its ensemble cast.

Lindsay Duncan has booked a role on the HBO drama's upcoming third and final season, which is set to bow sometime in 2017. In typical Leftovers fashion, the specifics of her part — even the number of episodes the Birdman actress will appear in — are being keep under wraps.

The enigmatic show from Damon Lindelof and Tom Perrotta recently wrapped the initial stages of filming on its upcoming season in Texas and has since relocated to Australia, where it will finish out production on the series. The 2017 return date is in line with the timing of the show's first two installments — season one debuted in June 2014 and season two in October 2015.

Duncan, fresh off her turn in Disney's Alice Through the Looking Glass, will join returning Leftovers castmembers Justin Theroux, Amy Brenneman, Christopher Eccleston, Liv Tyler, Chris Zylka, Margaret Qualley, Carrie Coon, Janel Moloney, Kevin Carroll, Jovan Adepo, Regina King and Scott Glenn. The Scottish-born actress previously appeared in Sundance TV's Maggie Gyllenhaal vehicle The Honorable Woman and can next be seen alongside Alfie Allen and Angela Bassett in the miniseries Close to the Enemy, which will debut later this year on Starz.

In an essay for The Hollywood Reporter, showrunner Lindelof recently addressed the show's impending finale. "More than anything else, I want to approach the ending of The Leftovers with confidence. Even if we fall flat on our faces and everybody hates it, it’s better than hedging or trying to be all things to all people or saying we’re going to be one thing and then at the last minute basically cut bait and be another thing," he wrote. "People want consistency in the storytelling."