Hey so, not too much info floating around tbh:

• Heart of Darkness” – Mary Margaret hires Mr. Gold as her attorney when Emma is forced to arrest her for the suspected murder of David’s wife, Kathryn. Meanwhile, back in the fairytale land that was, Prince Charming sets out to stop a determined and unhinged Snow White, whose memory is still clouded by Rumplestiltskin’s potion, from assassinating the Evil Queen
• promo pictures HERE

There weren’t really any spoilers released because there weren’t any major castings to get sides from and not really any pictures from set. Sorry not to be of more help.

-Rita