There are spoilers for 4.18 "Heart of Gold" coming, so if you haven't watched it yet, steer away!!!
"Once Upon a Time" has come under a lot of criticism over the past two seasons. Some of it I have agreed with, although for the past four episodes I've been clearing noting and stating a definite trend upwards in quality. Episode 18, "Heart of Gold" not only continues the rise in quality, but also pays off something set up at the end of Season 3 and fixes a continuity issue that we weren't even expecting to get explained.
Let's talk about that first. Several seasons ago, when Robin Hood was first introduced as a one-off character, he was portrayed by an actor that made us all go "meh." When the character came back as a series regular, he was recast as Sean McGuire, who was so superior that all the fans breathed a sigh of relief and decided not to nitpick the change of face. Recasting just happens sometimes, and outside of Doctor Who, we mostly just accept it without being given any explanations.
"Heart of Gold," however, not only explains that face change, but uses the masking device to explode our minds with the revelation that Zelena switched places with Marian before Emma took her out of the Enchanted Forest.
We knew Zelena and Oz would be making a return to the screen from the most recent TV teaser, but there was no indication why or how. Season 3's finale had certainly left the possibility that Zelena didn't actually die, but with neither hide nor hair of her showing up in the first half of Season 4, I pretty much figured that was just another lost thread in the entertaining but messy tapestry that is "Once Upon a Time."
And here we thought the Queens of Darkness were a red herring for the Author... while both the queens and certainly the Author are still relevant to the plot, they both pale in comparison to revelation that the real threat isn't even Gold, it's Zelena, the grand puppet-mistress.
I had no idea how they were going to deal with the Regina/Robin/Marian triangle without being cheesy or a cop-out, but this is brilliant. I love it.
(Also, any time Will Scarlet gets to do anything on screen is a time for cheering, so multiple flashback scenes were a real treat!)
BUT now we have to wait a week to find out what answer Regina is going to give Gold. And man, but Lana Parrilla is just superb at bringing Regina to life. My heart just breaks for her!