Emma has been at the mercy of Regina too long in Once Upon a Time.  But tonight, with the help of an unexpected ally, she decides to fight back.

Sidney approaches Emma in tonight's episode and reveals some new details about his life: he believes that Regina got him fired from Storybrooke's newspaper and also used him as a pawn in the sheriff election, which humiliated him.  After losing the election, and while in the process of writing an expose on the mayor's office, he lost his job.  But he uncovered some valuable information that he says Regina doesn't want anyone to know.  Initially, Emma is hesitant to believe him, thinking he's just drunk and bitter.  Later, the pair meet again and Sidney reveals some additional information that may convince Emma to partner with him.

It also looks like Henry will be suffering a set-back when he loses his special book of fairytales. We also know, from a sneak peek posted a few days ago, that Mary Margaret and David will continue to see each other after their kiss at the end of the last episode.

Meanwhile, Snow White, her father and the Queen are the focus of the fairytale story.  Once Upon a Time is flashing back to a time when King Leopold was still alive and we'll be getting a lot of insight into the Queen's hatred and jealousy of Snow White, which is particularly displayed when Leopold fawns over his daughter and seems to ignore his wife (which can be viewed in this sneak peek).

Watch three additional sneak peeks for tonight's Once Upon a Time below, beginning at 8:00 p.m. EST on ABC.