“Forrest Gump” star Gary Sinise has signed on to join the fourth and final season of Netflix’s YA series “13 Reasons Why.”

Sinise will play Dr. Robert Ellman, who Netflix describes as a “a compassionate, incisive, no-nonsense adolescent and family therapist who works to help Clay Jensen (Dylan Minnette) battle anxiety, depression, and grief. Ellman helps guide Clay to accept the help he needs and come to terms with the trauma in his past.”

Season 4 is currently in production and will feature the core cast’s graduation from Liberty high. A premiere date has not yet been set.

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In the mean time, the third season is set to launch on Aug. 23, and will center on the surprising death of another high school student at Liberty: Justin Prentice’s jock Bryce Walker. You can watch the trailer here.

Here is the official description for season 3:

Eight months after preventing Tyler from committing an unthinkable act at Spring Fling, Clay, Tony, Jessica, Alex, Justin and Zach find ways to shoulder the burden of the cover-up together while helping Tyler move toward recovery. But when the aftermath of a tumultuous Homecoming game culminates in the disappearance of a football player, and Clay finds himself under police scrutiny, it’s up to a shrewd outsider to steer the group through an investigation that threatens to lay bare everyone’s deepest secrets. The stakes are raised in this riveting third season of ’13 Reasons Why,’ as the consequences of even the most well-intended actions can alter a life forever.

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“13 Reasons Why” Season 3 stars Minnette as Clay Jensen, Brandon Flynn as Justin Foley, Prentice as Bryce Walker, Alisha Boe as Jessica Davis, Christian Navarro as Tony Padilla, Miles Heizer as Alex Standall, Devin Druid as Tyler Down, Ross Butler as Zach Dempsey, Timothy Granaderos as Montgomery de la Cruz, Anne Winters as Chloe, Steven Weber as Principle Bowen, Brenda Strong as Mrs. Walker, Amy Hargreaves as Mrs. Jensen and newcomer Grace Saif as Ani.

The Paramount Television-produced series was created by Brian Yorkey who executive produces with Joy Gorman, Mandy Teefey, Kristel Laiblin and Selena Gomez.

Season 3 of “13 Reasons Why” premieres Aug. 23 on Netflix.