• Actress Viola Davis, winner of the award for Outstanding Performance By a Female Actor in a Drama Series for 'How To Get Away With Murder', attends The 22nd Annual Screen Actors Guild Awards at The Shrine Auditorium on January 30, 2016 in Los Angeles, Cal

Actress Viola Davis, winner of the award for Outstanding Performance By a Female Actor in a Drama Series for 'How To Get Away With Murder', attends The 22nd Annual Screen Actors Guild Awards at The Shrine Auditorium on January 30, 2016 in Los Angeles, Cal (Photo : Getty Images/ Rich Polk)

Showrunner Pete Nowalk confirmed at the Television Critics Association summer press tour that "Grey's Anatomy's" Amy Madigan and "NYPD's" Esai Morales will appear in "How To Get Away With Murder" Season 3 as guest stars. Main lead Viola Davis recently hinted about the new mystery that Annalise Keating and the Keating 5 will be dealing in the new season of the legal drama TV series.

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In an interview with TVLine, Nowalk said that Madigan and newbie Morales will be appearing in one of the episodes of the new season. Nowalk did not elaborate which episode it is, and what will be their respective roles in "HTGAWM" Season 3.

Madigan is a recurring cast who recently finished her stint in "Grey's Anatomy" as psychiatrist Meredith. Morales was last seen in several TV series, including "From Dusk Till Dawn: The Series," "Criminal Minds," and "Mozart in the Jungle."

Aside from the Madigan and Morales, it was earlier reported that "Dexter" alum Luna (Lauren) Vélez will be joining in "HTGAWM" Season 3. She will be playing an unnamed character, who will be the president of the Middleton University, where Annalise Keating works as a legal professor.

Earlier teasers revealed that the upcoming season will have a new mystery, which will start from Lila's death in the initial episode of Season 3. Davis believed that the mystery is unbelievable that it is going to cause trouble for everyone.

"Yeah, he's presenting a new mystery, and it's going to be presented very quickly in the first episode," Davis told Deadline. "But with that new mystery, he explores the relationships in a much deeper way."

There are also some predictions that "HTGAWM" Season 3 will see some flashbacks and more hacking activities of Oliver (Conrad Ricamora). The death of Wes Gibbin's (Alfred Enoch) father will also be touched in the new season, and Wes will be in a bit of  depression after his father was shot in front of him.

"HTGAWM" returns on Sept. 22. Watch Davis' interview where she talked about the new mystery in the new season: