Emma (Jennifer Morrison) will be dealing with a "side effect" in her attempt to stop Hyde (Sam Witwer) in the season 6 premiere of ABC's Once Upon a Time.

The season 6 premiere of Once Upon a Time is titled "The Savior", which is appropriate considering the concept of being "The Savior" will be the focus of the early parts of season 6. We got a tease of Aladdin (Deniz Akdeniz) being another Savior in a clip from Comic-Con and with Emma as the present-day Savior, it's safe to assume this will a major theme in the premiere.

ABC has released the plot synopsis for the premiere, revealing that Emma will develop some type of "side effect" in dealing with Hyde while Regina (Lana Parrilla) and Zelena (Rebecca Mader) become roommates.

"In the season premiere episode, 'The Savior,' as our heroes set out to stop Hyde, Emma develops a mysterious side effect, and Storybrooke becomes a haven for refugees from the Land of Untold Stories," the synopsis reads. "Meanwhile, Regina and Zelena embrace their newfound sisterhood by becoming roommates, while Rumple [Robert Carlyle] tries to free Belle [Emilie de Ravin] from the sleeping Curse with the help of a stranger. In flashback, Jafar [Oden Fehr] confronts an afflicted Aladdin in Agrabah, and a secret about the Savior is revealed."

Guest stars for the premiere episode include Witwer as Hyde, Raphael Sbarge as Archie Hopper/Jiminy Cricket, Beverley Elliott as Granny, Oded Fehr as Jafar, Deniz Akdeniz as Aladdin, Tarun Keram as Emir, Peter Marcin as Chief, Farris Tyab, Jordan Ashley Olson as Young Nurse/Oracle, Giles Matthey as Morpheus, Thomas Gasior as Musketeer #1, Ingrid Torrance as Nurse Ratchet and Hank Harris as Dr. Jekyll.

Once Upon a Time season 6 premieres Sunday, Sept. 25 at 8 p.m. ET/PT on ABC.

Watch the teaser for the very first scene of the premiere below: