Alex O'Loughlin, Chi McBride Alex O'Loughlin, Chi McBride

It's no secret that SWAT Captain Lou Grover (Chi McBride) doesn't always see eye to eye with McGarrett (Alex O'Loughlin) on Hawaii Five-0. But that may change on Friday's Season 4 finale (9/8c, CBS), when Grover finds his professional ethics are put to the ultimate test.

"He starts off the season looking at what McGarrett's doing as being unorthodox. It's everything he hates," showrunner Peter Lenkov tells "[The finale] brings everything full circle. ... Grover's put into a situation where he's got to act the same way, and I think he sort of learns a lot about himself and gains a new respect for McGarrett through the course of that story. He sees that sometimes you have to play dirty in order to get the bad guys."

The "bad guys" in this case, are represented by the return of computer hacker Ian Wright (Nick Jonas), who orchestrates the kidnapping of Grover's daughter. Especially observant fans may recall that their ominous encounter was actually telegraphed in an earlier episode this season.

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"There was a line that may have been seen like a throwaway line in the earlier episode [Jonas] was in this year, where Grover and McGarrett take him to the gate and he's just about to board the plane," Lenkov explains. "He hands back a laptop that was Grover's daughter's laptop. And he says, 'Tell your daughter thanks for her laptop. Hopefully one day I'll get to meet her.' ... That line is very important in the finale, because he does get to meet her. And things go very bad."

Longtime villain Wo Fat (Mark Dacascos) also makes a surprise appearance in the finale, in a scene Lenkov hints will be "surprising and very pleasing to people that have been watching the show for years."

But Grover's plot line will be the main focus of the episode and will set up some interesting future developments for the character. With his daughter's life on the line, Grover finds himself on the other side of the law — and his actions will definitely have consequences. But they may not be of the nature fans will expect.

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"It ties in thematically to the first episode of the season. It puts Grover in a situation where he's got to be McGarrett," Lenkov says. "And as sort of renegade and out of control as [Grover] may have thought McGarrett was in that first episode, he goes even further in this one. And there's going to be repercussions for that. You can't just do that. Five-0 could get away with it, but Grover can't. Grover's part of the HPD. ... He doesn't have a free pass like Five-0 does."

Suffice it to say, Grover will find himself in a very different position heading into Season 5 than he did at the start of Season 4.

"We're really trying, with the first episode and the last episode, to really make it almost like Grover's bar mitzvah," Lenkov says. "He really grows up through the course of the season, but he really sort of sees that McGarrett's way of doing business may not be so bad after all, if the stakes are that high. ... Sometimes you have to turn the badge around to get the job done."

The Hawaii Five-0 Season 4 finale airs Friday at 9/8c on CBS. Catch up on the latest episode here.

(Full disclosure: is owned by CBS.)

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