It's What's Inside Ending Explained: Cast Breaks Down What Happens

When Alycia Debnam-Carey, one of the stars of "It's What's Inside," finished the script for the first time, she had a strong reaction to the ending.

"What? Wait, what did I just read? What happened? It was so confusing that I had to read it three times before I started talking to the director about it," she tells TODAY.com. "It's so complicated. There are so many moving pieces."

The new thriller, which arrived on Netflix Oct. 4, centers on a group of friends from college reuniting before the night of a wedding. There, they play a dangerous, and confusing, game — one that also sent the cast reeling.

"Keeping track was pretty hard," she says.

Below, Debnam-Carey and other cast members break down the movie's ending.

Meet the main characters and their body-swapping game The movie opens by introducing our main players, a friend group from college.

Reuben (Devon Terrell), the groom, cuts his fiancée loose for his last night as a single man for one last hurrah in the old mansion he inherited from his mother.

Shelby (Brittany O'Grady) and Cyrus (James Morosini) have been dating since college, but are experiencing relationship and intimacy problems, despite the fact that everyone thought they would be engaged by now.

The rest of the reunited friend group includes:

Trust fund baby-turned-rapper Dennis (Gavin Leatherwood)

Hippie Maya (Nina Bloomgarten)

Misunderstood artist Brooke (Reina Hardesty)

Self-obsessed influencer Nikki (Debnam-Carey), whom Shelby envies and Cyrus worships.

The night is going as expected until their estranged friend Forbes (David Thompson), who had been expelled from their college for drama at a party involving his sister Beatrice (Madison Davenport), unexpectedly arrives with a briefcase and a devilish smile.

Opening up the briefcase, Forbes tells the group that he created an "experience" involving electrodes and some other sketchy technology that he wants them to try.

Turns out the machine allows everyone at the party to swap bodies — each participant keeps their own mannerisms, thoughts, and feelings, but in the body of one of their friends.

Thompson tells TODAY.com he was excited to play Forbes.

"It was such a treat to see that I get to be the inciting incident. I get to be this weird outsider that comes in and shakes things up and then immediately jumping into someone else's perspective and then having to deal with the consequences of the thing that I've just brought," Thompson says.

What happens during Round One? During the first round of the game, it becomes apparent that there's some long-simmering sexual tension between multiple members of this friend group.

Cyrus is in Reuben's body, but at Forbes' suggestion, he tells everyone he's actually Forbes as a way to explore "new opportunities."

By lying, Cyrus, as Reuben, is able to approach the body of Nikki (who is actually Maya) and live his fantasy of kissing her. Meanwhile, Maya has a long-standing crush on Reuben.

This kiss lets both Cyrus and Maya get physical with the bodies of the bodies of the people they are attracted to.

What happens during Round Two? How two characters' deaths complicate things Round One is enough fun that the group agrees to a second round — and that's when things go truly haywire.

Reuben, set to be married, is still longing for Maya. While in Dennis' body, Reuben approaches Maya's body (who is occupied by Brooke). The two get physical on a balcony, which breaks. They both fall to their deaths.

That means two souls are now trapped in bodies that aren't theirs — forever. Dennis is in Cyrus' body; Maya is in Shelby's body. The spirits of Reuben and Brooke are gone.

From there, the characters scramble to manipulate each other. Some want to stay in their new bodies — like Shelby, who is in Nikki's body — and some are desperate to return.

Still in Nikki and Forbes' bodies respectively, Shelby and Cyrus use this moment to work out their relationship woes. Shelby confronts Cyrus about his college crush on Nikki and he insists that he never considered Shelby to be the "consolation prize."

Meanwhile, the police are on their way, and Dennis, in Cyrus's body, confesses to the murder.

"We all were creating our characters together," O'Grady, who plays Shelby, tells TODAY.com. "We all kind of studied one another as we were in our process ... and there's this mutual respect when it came to everyone making sure they felt like they were giving the other character justice that someone else created."

Wait, who was Forbes? Inside Beatrice's final twist and what happened at the birthday party The final act of the movie takes place the next morning and re-introduces Beatrice, Forbes's sister. Beatrice appears the day after the party — and reveals she is actually Forbes.

That means Forbes was actually Beatrice all along. This was Beatrice's way of getting revenge on the friend group for what they did to her in college.

Back in the day, Beatrice was hooking up with Dennis — even though she was in high school, and even though he was dating Nikki. Drama escalated at a birthday party. While there, they hooked up again, and she told everyone they were in a relationship.

Dennis, meanwhile, denied what she was saying and told everyone else Beatrice was crazy. Forbes and Dennis got into a fist fight that ended with Forbes getting expelled.

In the aftermath, Beatrice struggled with mental health crises and went to a psychiatric care facility. After Forbes introduced her to his machine, she formulated a revenge plan.

"I remember reading it and thinking something is amiss with this guy, and you can't quite tell what he's getting at," Thompson says of his first encounter with Forbes. "Then you see the genius twist. It's unexpected but inevitable."

Where does each character end up? Beatrice ends up getting revenge on the people who hurt her. She arguably ends up the winner of this body snatching game. She takes Nikki's body and Dennis' money and escapes.

As for the rest of the characters? Here are the final positions.

The spirits of Reuben and Brooke are dead. The bodies of Dennis and Maya are dead.

Forbes is in Beatrice's body, where he was the whole time.

Nikki is in Reuben's body. Sophia shown crying on the morning of the wedding, meaning that Nikki — as Reuben — ran away.

Dennis is in Forbes' body.

Maya is in Brooke's body.

Cyrus is in his own body — and is in jail, having taken the fall for Brooke and Reuben's deaths.

Shelby is back in her body.

Shelby and Cyrus appear to break up. Shelby goes to visit a desperate Cyrus in prison — remember, Dennis, who was in his body, confessed to murder.

As he pleads for her help and questions who she really is, Shelby stays stone cold. In a classic Cyrus speech, he tries to say what he thinks Shelby wants to hear in order to get her to fold. She doesn't.

O'Grady said she believes that Shelby's future post-Cyrus is bright.

"I think she goes to therapy," O'Grady says. "I do not think she gets back together with Cyrus. I think she moves on and probably finds a whole new group of friends, a whole new life and starts over."

Debnam-Carey hasn't lost hope for Nikki, either — even though she's trapped in Reuben's body. She thinks Nikki turns Reuben into an influencer as successful as her old self once was.

"That's his new career path. He's like, 'Sorry, I'm not getting married and I'm moving to LA and I'm becoming an influencer," she says.

Will there be a sequel? Debnam-Carey says she and other cast members are open to returning to their characters (or their bodies).

"There are some really fun sequels that could be springboarded from that point. We're all excited — this should have a sequel," she says. "Nikki's clambering to get back into her own body. There's a lot of opportunity there."

While she would "100% come back," she confirms there have been "no actual conversations" about a sequel.

"I think it was such an incredible experience. It's such a unique movie. I've never seen anything like it."