'Once Upon a Time' Season 3 Spoilers: 2 New Characters Featured in 'Kansas' (TRAILER VIDEO)

(File: ABC/File)

"Once Upon a Time" viewers will certainly want to tune in this week, as Mary-Margaret/Snow White finally gives birth to her child and a visitor from Kansas drops in on the witches of Oz. It's the last episode before the two-hour finale, and tensions have never been higher in the town of Storybrooke.

Mary-Margaret finally gives birth to her second child, but will she actually be able to keep the child safe once Zelena learns of his/her birth? The Wicked Witch descends upon the hospital, but Regina and the rest of the town work to keep the infant safe from her grasp. How long can they hold her off, though, given her determination to have the child?

Meanwhile, in the past, Glinda the Witch of the North attempts to convince Zelena to use her powers for good, not evil. It's a storyline very familiar to fans of "Wicked" the book and the musical. But a fresh face threatens to destroy Zelena once and for all after a tornado somehow transports a girl named Dorothy to Oz. Her appearance makes for a unique twist that audiences are sure to enjoy, as she is a serious threat to the Wicked Witch.

Viewers will finally have a full episode with the "original" Henry, who finally received all of his memories last week. How will he contribute to the battle against evil? And what will Hook do now that Henry is back to his normal self and he is still hostage to the curse placed on him by Zelena? These questions and more will have to be settled in the final three hours of the season, which are certain to be jam-packed with action.

The show's finale, entitled "There's No Place Like Home," leaves plenty of answers for viewers to ponder until its airing on May 11. With all that has happened this season, whose home will the residents of Storybrooke be returning to? And what new adventures face them?

"Once Upon a Time" airs Sunday nights on ABC.

Watch the promotional trailer here: