Hawaii Five-0 type TV Show network CBS

As Kono (Grace Park) prepares to head down the aisle in the Hawaii Five-0 season finale, a familiar face will rejoin the team when a nuke is located on the island. But does Catherine’s (Michelle Borth) arrival only serve to give McGarrett (Alex O’Loughlin) closure, or could there actually be a future for them? EW tracked down executive producer Peter Lenkov to get the scoop on the season finale:

ENTERTAINMENT WEEKLY: So, you had to ruin Kono’s wedding day with a nuke, eh?

PETER LENKOV: I wanted to do a story where literally just before the wedding takes place, I wanted our guys to do something big. Just the idea of our guys—McGarrett, Danny (Scott Caan), Chin (Daniel Dae Kim), Grover (Chi McBride) and even Kono as she’s prepping for her wedding—in tuxedos saving the day, very much much like a James Bond movie. The idea was to do something with big stakes and have our guys in tuxedos, because really on the way to the wedding something happens that causes them to take a detour.

This is loosely based on a real story where a nuke transport went off the grid for a few hours. This happened about 10 years ago. The idea is that a nuke is stolen from an unmarked transport and brought to the island. We believe it’s about one thing and it turns out to be something other than we first thought. All the while, all we want to do is stop this thing, get it into the right hands and still make it to Kono’s wedding on time. While Adam (Ian Anthony Dale) and the guests are waiting for the wedding to begin, this is all taking place. It’s a really fun, exciting, edge-of-your-seat episode.

Will the team have to cross some lines to get things done?

Yeah. One of the fun things that we used to do in the first season is seeing McGarrett really take advantage of the immunity and means that he got. They’re trying to do something that’s going to save a lot of lives, so they’ll do whatever it takes. They definitely cross some lines.

With Catherine coming back, is this your way of giving McGarrett closure?

There’s not closure in that particular episode. We’re going to get to that. The whole idea, always from the beginning, was to rip those two apart and have a reunion at some point. Whether she stays or not, that’s ultimately to be seen. The idea was to do it at the end of the season, have her show up not necessarily to reunite with McGarrett, but she comes for Kono’s wedding.

So you’re saying there’s a chance she could be back next season?

Sure, anything is possible. That’s to say we come back next season.

How does McGarrett feel about her return?

Everybody around him is very protective because it looked like she just left and broke his heart, but I think he saw what she was doing was very righteous and honorable. He believed she was staying in Afghanistan for the right reasons. It’s hard. It’s awkward. There’s a running gag in the story where Danny is pressing him to have a talk with her about, “What’s your intentions? Are you going to stay? Are you going to run away again?” Hopefully that’ll be a fun run. Seeing McGarrett vulnerable is interesting. His heart was broken. He doesn’t necessarily wear it on his sleeve, but you’ll see shades of that in the finale.

Is there anything on the Ellie (Mirrah Foulkes) front, since we haven’t seen her in awhile?

She wasn’t a regular. She was semi-recurring. She was a good resource for McGarrett. It was good for him to have a female friend. She tried to set him up and hopefully that will pay off in future episodes down the road. McGarrett is definitely open to a relationship if it doesn’t work out with Catherine. She’s still part of our world.

Will we see Ellie meet Catherine at all?

I hope so.

Will we see a confrontation between Gabriel (Christopher Sean) and Chin in the finale?

For sure. That definitely plays into our finale, and hopefully into future episodes of our show. He’s definitely a person who we like as an actor and as a person. He’s good for the show. He’s definitely going to be a presence in our lives.

Danny’s ex-wife Rachel (Claire van der Boom) returns in the first hour of the finale and reveals something big. What can you tease?

Just that it’s a shocking secret. Just the shock of her being back on the show is enough. I noticed people were speculating online. A couple people were getting close to what the story is, but for the most part, people are not getting it, which is a good thing. The hardest thing when you’re writing is to surprise people. It’s a good turn for the story. It’s actually good growth for Danny as a character. It will play into future episodes of the show, and it launches a new storyline for his character. I’m excited about that. It’s not just bringing her back as a special guest as a gimmick. It’s bringing her back to launch a new storyline.

Is she coming back to reveal she’s had another one of Danno’s children?

[Laughs] Here’s the thing: It’s a surprise and I’m hoping it’s unexpected.

Whatever happens with the secret, does it put a damper on the flirtation we’ve seen between Danny and Dr. Shaw (Amanda Setton)?

No, I don’t think so. There is great chemistry there and it would be nice to explore that relationship. Whether it goes further or just really good friends, that’s something to see. I actually like those two together a lot.

Will we find out what’s going on with Doris (Christine Lahti) in the finale?

The Doris thing I’m still keeping open, but there is definitely advancement in a lot of the threads of other stories, for sure.

Is there a cliffhanger in the season finale?

There’s a semi-cliffhanger. It’s not a traditional cliffhanger. It’s more of a character-driven cliffhanger. Last year we didn’t do a cliffhanger, but the three seasons before we did big stakes cliffhangers. I wanted to do something character-wise where the audience will say, “Holy crap. I’ve got to come back and see the next episode.” Things are going to get pretty hairy.

Hawaii Five-0’s two-hour season finale airs Friday at 9 p.m. ET on CBS.