Season Six of 'Dexter' has already shown it has two intriguing, disturbing and creepy "Big Bads" working for it in Travis and the Professor. They're murdering people in bizarre ritualistic ways and their storyline was the most compelling part of this episode, yet frustratingly, Edward James Olmos and Colin Hanks were only given a few minutes of screen-time. Using an abandoned temple as an evil lair, they orchestrated a grotesque final scene that made the Headless Horseman look quaint, sending a chopped-up, half-murder-victim, half-mannequin riding on two horses through a Miami block party.

Still, at this point it's unclear exactly what specific kind of twisted cult ideology is driving Travis and Professor Gellar's murderous weirdness. It feels like we should know by now, but I guess we're still in the weird ritualistic storytelling phase of this season's plot set-up. It's something about repentance and purity, but that lack of info is starting to walk a dangerous line between suspenseful and feeling like it's overdue. As Travis put it, "I don't believe what you are saying."

'Dexter' opened this episode by extolling the importance of ritual, which for our beloved serial killer of serial killers involves reading Harrison a bed-time story and then promptly slicing a bad guy's throat. All in a day's work.

This was a low-kill count episode (just 1!) that instead focused on introducing Mos Def's Brother Sam character, setting up new developments for Deb and conflicts at Miami Metro, and letting the religious creepiness of Travis and Professor Gellar simmer on low heat.

Rapper-turned-actor Mos Def is the latest addition to 'Dexter' as the Showtime series adds to the cast for its sixth season.

Mos Def's multi-episode arc will see him play a born again ex-con who "seems to continually find himself surrounded by violence," according to The Hollywood Reporter. As expected, Dexter "will reveal the truth of who he really is."

The actor joins Colin Hanks as one of Dexter's season six nemeses.

In other TV news ...

• Will Smith and Jada Pinkett Smith will appear on the 'Oprah' finale. The husband and wife team will chat with Winfrey as she says goodbye after 25 years. The final episode is scheduled to air on May 25. [TV Guide]

• Seth Gabel has been promoted to series regular on 'Fringe.' The 'Dirty Sexy Money' actor has recurred on the Fox sci-fi drama for the past two seasons as Lincoln Lee. [TV Line]

• 'Falling Skies' hasn't even premiered yet and already TNT is considering a season 2. The network is reportedly looking to hire a showrunner for the potential second season. [Deadline]

Actor/rapper Mos Def has joined HBO's upcoming comedy series 'Enlightened,' Deadline.com reports.

The series will star Laura Dern as a self-destructive woman who has a spiritual awakening and decides to live an enlightened life, turning her work and family life upside-down. Mos Def will play her new boss when she returns to work.

This will be Mos Def's first full-time series.

Mos Def: not exactly a bad ass rapper. Sure... he was arrested in New York City, but it's not for your usual rapper garbage like gun possession (Diddy) or lying about a murder (Lil' Kim). Nope, NYC police cuffed Mos Def for an impromptu performance he gave outside the Radio City Music Hall last Thursday before the MTV VMAs. Apparently he didn't have a permit for the sound system. The cops interrupted a song he was performing about Hurricane Katrina on the back of a flatbed truck outside the awards show. Police kept Mos Def overnight and now he'll have to appear in court.