These are things we know about 5x05:
*It's a "heartbreaker" that will blow up Twitter.
*Emilie told fans that they'd like the episode, so that possibly implies that Belle or RB will be featured.
*The title implies something to do with memories or nightmares.
As an exercise, let's try to think of all the things that could possibly, realistically make this ep a heartbreaker.
*I think the most obvious is that this is the ep where we see why Emma gives in to the Darkness.
*There's the theory that Emma removes everyone's memories of her.
*Somebody dies. I don't know why, other than wishful thinking, but some SQers seem convinced that Hook is going to die in this ep. I sincerely doubt it. It's possible that Dark Swan could kill somebody. If that's the case, it would probably be a recurring character or one of the Camelot characters. I really don't want Emma to kill anybody, because it would destroy her once she's herself again. (Unlike Regina, she would actually regret killing someone.)
Anyone else?