The producers of ABC's Once Upon a Time are working out the overall theme from season 5, but they already have a one-word description for it.

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Once Upon a Time co-creator (and co-showrunner) Edward Kitsis spoke with Zap2it recently and teased a description of season 5. The executive producer simply said "Swan," and while this seems like an obvious allusion to Emma Swan (Jennifer Morrison), it doesn't necessarily confirm it.

Regardless, Once Upon a Time fans were left with quite a tease in the season 4 finale, with Emma succumbing to the dark side and becoming "Dark Emma." It is not known if Emma will become the new "big bad" of the series in season 5, but it's possible she could go through an experience similar to the famous ballet Swan Lake. The conflict between the Swan Queen and the Black Swan featured in the ballet could represent Emma battling with her new dark side.

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The producers actually have not worked out the full theme of season 5 year, though planning is beginning in the summer.

"We start with a theme we want to explore and go from there," Horowitz told Zap2it. "We've done our mini-camp. We actually have the next month so we like to sit for the next month and ask 'Does it still hold true?'"

Once Upon a Time season 5 is set to premiere on Sunday, Sept. 27 at 8 p.m. ET/PT on ABC.