We're constantly looking for clues about what's coming up next on Once Upon a Time Season 2, especially now that we're headed into the finale, Season 2, Episode 22: "And Straight On 'Til Morning" (May 12).  What better source of info than the promo itself?

The episode preview tells us a fair amount about what's going to happen in the season ender, so we took a close look to find out exactly what we can expect.

Destroying Storybrooke. The promo opens with a scene you can see more of in this sneak peek. Hook questions Greg and Tamara's plan to destroy Storybrooke, and Greg responds that they're willing to die for their cause.

The curse is activated. Next (and again, this is expanded on in the sneak peek) we see Greg swing an axe and hit the black diamond, activating the trigger.

The effect of the trigger. And clearly, this thing is a big deal. We see an earthquake, townsfolk running and screaming, and vines crawling up buildings. The situation is clearly desperate.

Can the trigger be stopped? "There is no stopping it," Regina warns. But there is slowing it down — a painful-looking task Regina herself takes on. But will she be able to contain it for long enough to save everyone?

Henry's distress. At :21, we see Henry ask in distress, "where's my mom?" If this scene is after Regina has gone down into the mines to hold back the trigger, we expect the answer to this question to be painful for Henry to hear.

Rumple upset. At :23 we see Belle (er, Lacey?) hugging Rumple, and he looks very upset. Is it because of the town's imminent destruction, or is it over losing Bae?

A family moment. At :26 we see Charming hug Snow, Emma, and Henry to him. It looks like they're scared, but we're excited for this scene — it might be the touching Charming family moment we've been waiting for.

Explosion? The promo ends with the sound of an explosion, but who knows if that's actually from the show, or just added in for drama.

Check it out yourself:

Catch the episode on Sunday, May 12 at 8 p.m. ET/PT on ABC.

Rebecca Martin is an editor at Wetpaint Entertainment. Follow her on Twitter @BeccaDMartin.