Derek? Who's Derek? "Grey's Anatomy" is returning for its 12th season on Thursday, September 24 at 8 p.m. ET., and ABC just shared details on the premiere. The first episode, "Sledgehammer," will guest star Debbie Allen and Joy Lauren Adams and show Meredith Grey (Ellen Pompeo), Miranda Bailey (Chandra Wilson), Jackson Avery (Jesse Williams) and April Kepner (Sarah Drew) adapting to changes.

Here's ABC's synopsis for "Sledgehammer," which was directed by Kevin McKidd, aka Owen Hunt:

Grey Sloan Memorial springs into action to save the lives of two young girls whose powerful story will force some of the doctors to revisit the effects of bullying on their own pasts. Meanwhile, Meredith must adjust to changes at home with her new roommates while Bailey continues to fight for the Chief of Surgery position and Jackson prepares for April's return to Seattle."

Poor Meredith can never catch a break. She loses the love of her life and now she has roommate problems. (Ellen Pompeo said Meredith will be living with Amelia and Maggie, "throwing herself into her work and her kids" and possibly getting a promotion.)

Meanwhile, you may have seen that Patrick Demsey, aka McDreamy, is moving on and may be joining the world of Bridget Jones.

Are you excited/nervous for the changes ahead in "Grey's" Season 12?

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