So, what can we expect as Zelena works towards her wicked wishes? We've taken a closer look at the promo to see what it reveals.
1. Time travel! Well, Once Upon a Time is brought to us by writers who cut their teeth on Lost. Is it really a surprise that time travel eventually came up? At :02 Zelena tells someone she's planning to go back to "claim the life that I deserved." And yes, she does mean back in time, as Belle (Emilie de Ravin) explains at :06.
2. Is the spell already working? At :04 we see the sky filled with a swirling green spell. Is that the time travel spell in action? Zelena certainly looks happy about something at :06, so we have to assume her plans are going well.
3. Raising the dead! Our heroes apparently decide that to counter Zelena, they need to "raise the dead" (:08), though the promo might be misleading us on exactly what they're doing. Either way, Young Cora (Rose McGowan) is back, baby! "We have to talk to my mother," Regina (Lana Parrilla) explains at :10, sounding more exasperated than anything.
4. Flashback. Speaking of Young Cora, the show of her we get at :10 looks like a flashback moment to us.
5. Things get creepy. In completely unsurprising news, trying to talk to the dead leads to some completely creepy results. In the back half of the promo, see Regina and Snow (Ginnifer Goodwin) walking nervously through a house. Oh, and a door totally flies off its hinges at :20. Yeah, it looks like something has gone very wrong.
Check it out for yourself.
Did we miss anything important? Interpret something wrong? Let us know your thoughts in the comments below!
Catch the next episode of Once Upon a Time on Sunday, April 20 at 8 p.m. ET on ABC.
Rebecca Martin is an Associate Editor at Wetpaint Entertainment and our resident Game of Thrones, Pretty Little Liars, and genre TV expert. Follow her on Twitter and Google+!