'The Gifted': SPOILER Joins the Hellfire Club

The mutants drew a line in the sand in tonight's season finale of The Gifted. Some surprising characters then crossed over from one side to the other.

SPOILERS for The Gifted Season One finale follow.

Earlier in The Gifted, the Stepford Cuckoos revealed themselves. The Frost sisters are representing the Hellfire Club, which is in a stage of rebuilding.

The season finale took some major steps in returning the Hellfire Club to its former glory. The Frosts tried to get into the heads of several members of the Mutant Underground. They played on Blink's brief history with the Brotherhood, and they tempted Thunderbird with resources, but they focused most of their attention on Polaris.

In a previous episode, the Frosts revealed that Polaris' father was a king of the Hellfire Club. They never mention Magneto's name, but the mutant terrorist was a member of the club in the comics. The Frosts tempt Polaris to follow in her father's footsteps, and she gives in.

Polaris uses her magnetic powers to blow up an airplane with a US Senator and the head of the Hound program on board. Later, she catches up with the Mutant Underground and offers a place in the Hellfire Club to any of them. Fade, Sage, and Andy Strucker are among those who accept.

Showrunner Matt Nix explained to ComicBook.com what this moment means for mutants.

"Polaris takes this step because she loves Eclipse and she doesn't want to put the people that she cares about - and in a way she loves Thunderbird and she really cares about Blink and she's just lost Dreamer who was a good friend of hers," Nix says. "So, in the face of all that, she's doing this on behalf of the rest of them."

"For this first 13-episode run, we've already kind of exploring the idea that they're not exactly on different sides, the beginnings of the Hellfire Club and the Mutant Underground," Nix adds. "They're kind of working towards the same goals and they're in a position where they kind of need to team up. I mean, there's not a lot else they could do."

The Gifted will return to FOX in 2018.