Fans wondering why Fox announced last month it had stopped development on the X-Men-based drama "Hellfire" now have an answer: The project seemed more like a film than a television series.

The project, which would have involved a version of longtime X-Men foes the Hellfire Club, encountered its first stumbling block when co-creators Evan Katz and Manny Coto left in January to work on "24: Legacy." However, Dana Walden, co-chairman and CEO Dana Walden, says there was also a problem in the approach to the series.

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"We did see an early draft of Hellfire and there was a lot of work to be done," she told Slashfilm at the Television Critics Association summer press tour. "Manny and Evan were getting very busy with the new 24. At a certain point we all regrouped, together with Simon Kinberg and Bryan Singer and Lauren Shuler Donner and Jeph Loeb at Marvel and really made a decision. I would say if there was anything about 'Hellfire' that was not ideal for us, it felt like a show that wanted to live as a feature rather than really taking advantage of what television does best: exploring relationships and characters and smaller moments. It doesn't mean it can't feel like a big show but 'Hellfire' felt more like another installment of the features."

The network replaced "Hellfire" with another, still untitled X-Men project from "Burn Notice" creator Matt Nix that indeed focuses on characters and relationships. It centers on two ordinary parents who discovery their children have mutant powers, and must go on the run from the government.

"There will be some iconic characters but mostly this is about a new family," Walden told the website.

"We haven't really been able to tell everybody what the whole story is," Loeb, Marvel's head of television, teased to IGN. "They'll be able to see it, and when they do, it'll be really clear why those characters were chosen, where they are going, and what's going to happen."

The project, which received a put-pilot commitment from Fox, could air as early as fall 2017.