Spiro, who was last seen guest-starring on NBC's 'Harry's Law,' will appear late in the season. According to TVLine, she'll play an acolyte of Colin Hanks' and Edward James Olmos' characters.

In the new season, Hanks plays a student of Olmos's religion professor. The two embark on a murderous path based on religious ideology.

'Dexter' Season 6 premieres Sun., Oct. 2 at 9PM on Showtime.

In other casting news ...

Mekhi Phifer and Cheech Marin will guest star on 'Psych.' 'Torchwood' star Phifer will play Drake, a member of Gus' college a cappella group, "Blackapella." Marin will play Deacon Jones, Drake's mentor. [TV Guide]

Broadway actor Will Chase has joined the cast of 'Smash.' Chase will play Steven, a man from Debra Messing's character's past in the Broadway-themed mid-season NBC drama. [Deadline]

Raul Esparza has booked a 'A Gifted Man' role. The Broadway veteran will play the boyfriend of Patrick Wilson's character's dead ex-wife. [Deadline]