Credit: Video Still

So far, the previews for Grey's Anatomy Season 9, Episode 8: “Love Turns You Upside Down” (December 6) have made the episode seem fairly lighthearted, but this new promo puts a more dramatic spin on things.

The voiceover in this preview promises the episode "will expose a secret so big ... it will shock everyone."

What could that be? There are a lot of images of Meredith (Ellen Pompeo) and Derek (Patrick Dempsey) in this promo, so maybe it's just the news that Mer is pregnant. But maybe it's something darker.

Check it out and decide for yourself!

Credit: ABC Family © 2012 Disney ABC Television Group Photo: Grey's Anatomy Season 9, Episode 8 Promo: What Will "Shock Everyone"? (VIDEO)

For more Grey’s spoilers, click here.

Catch the next new episode of Grey’s Anatomy on Thursday, December 6 at 9 p.m. ET/PT on ABC.

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