'Hawaii Five-0' Season 4: Alex O'Loughlin on McGarrett's 'looming existential crisis' and working with Chi McBride

hawaii-five-0-s4-chi-mcbride-alex-oloughlin.jpgWhen we last saw Steve McGarrett on "Hawaii Five-0," he was pressing his nemesis Wo Fat for answers about why his mother had visited Wo Fat in prison and what her agenda really is.

He gets some answers in Friday's (Sept. 27) Season 4 premiere. First, though, McGarrett ( Alex O'Loughlin) has to get Wo Fat ( Mark Dacascos) out of prison. The cliffhanger from last season's finale plays out over the course of the premiere, and O'Loughlin says it kicks off a good-sized arc for his character.

"What we set up is, Doris McGarrett's gone again. This is one of the most important emotional beats for McGarrett," O'Loughlin said in an interview with Zap2it and a handful of other outlets earlier this week. "First of all, his mother lied to him. ... Then she comes back and says I'm sorry? It's like, what do you mean? So he kind of opens up that wound again, opens up his heart and trusts her and [now] she's doing it again. So I can't imagine the looming existential crisis that's following him around day in and day out.

"But the key in his mind to unlocking the secrets too all this stuff he can't figure out ... that everyone lied to him about all these years, is Wo Fat. He really believes there might be some kind of family connection, some kind of blood connection. He's kind of obsessed with that idea."

Steve's relationship with Catherine ( Michelle Borth) also gets more complicated in the coming season, O'Loughlin says. In Friday's premiere, Catherine is abducted in the middle of a crisis, forcing McGarrett to make a really tough choice. And starting Oct. 4, Catherine's ex-boyfriend Billy Harrington ( Justin Bruening), who appeared briefly in the Season 3 finale, returns for several episodes.

"[Billy] comes in and causes a bit of a stir," O'Loughlin says. "So we see another side of McGarrett. ... He thinks he's keeping it under wraps, he's like 'I'm totally cool.' He's not cool at all. He's simmering on the inside."

On top of all that? McGarrett immediately gets off on the wrong foot with the Honolulu PD's new SWAT team commander, Lou Grover ( Chi McBride, playing a character who first appeared on the original "Five-0").

"Grover comes in and he cannot believe this immunity and means thing McGarrett's got with the governor, that he gets away with what he gets away with," O'Loughlin says. "He's so by the book -- he's appalled and angered and wants to change it. McGarrett is annoyed by this guy's presence: He's like, who is this guy? I get the job done -- who is he to tell me how to do the job?"

McBride will be back later in the season as well, O'Loughlin says: "I just read episode 8, and I'm up to page 50, and we just argued for 47 of the 50 pages. So they're really getting into it with those two characters."

"Hawaii Five-0" premieres at 9 p.m. ET Friday on CBS.
Photo/Video credit: CBS