As previously reported, Hanks is set to appear in all 12 episodes of the season and will play Travis, "a highly intelligent expert on ancient artifacts who gets linked to a series of grisly murders in Miami."
The Showtime series stars Michael C. Hall (Cabaret, Chicago, Skylight) in the title role and in the fifth season, according to Showtime, "Dexter [went] from happily married husband to guilt-ridden single dad." Dexter deals with his loss, a new relationship and his need to kill, which "overpowers his desire for human connection."
Olmos was nominated for a Tony Award in 1979 for his performance in Zoot Suit.
Mos Def and Hanks are both Theatre World Award winners for their performances in Topdog/Underdog and 33 Variations, respectively.
The sixth season is set to debut in the fall. For more information and show times, click here.