Danny (Scott Caan) and McGarrett (Alex O'Loughlin) get a lot more than they bargained for on Friday's Hawaii Five-0, when McGarrett accidentally signs them up up for a couples retreat.

"We set up a couple years ago that they had to do this mandated-by-the-governor therapy," Hawaii Five-0 showrunner Peter Lenkov explains. "They had to do a certain amount of hours a year, and McGarrett had the great idea of doing it all at once over a weekend. But he didn't realize that he had actually booked a couples therapy retreat."

But the honest mistake actually ends up having some positive effects on the longtime partners' relationship, according to Lenkov.

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"They have to do a lot of relationship bonding exercises," Lenkov says. "They really just have to spend a lot of time together in an intimate setting. It's fun, [but] there are some weighty moments in it as well. They don't work out any differences, but they do talk about some of their differences. So it's not all just hijinks."

It's safe to say that the bromance between Danny and McGarrett will be taken to a whole new level when all is said and done. "I think the audience is going to have a huge smile on their face when it's done," Lenkov says.

In addition to the couples retreat storyline, we'll finally get a glimpse into Kamekona's (Teila Tuli) past - for better or worse. "We've always established that he had this backstory where he was in prison before we knew him as this huggy bear, lovable guy," Lenkov says. "But we're going to see a lot of his past and what led him to being the guy that we know today."

Check out a sneak peek of the episode here:

Hawaii Five-0 airs Friday at 9/8c on CBS.

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