I don't know... while in theory this episode should have been a total winner for me, there were a few things that just didn't fully click. It wasn't bad by any means, but I just feel... sort of disheartened. Let's talk about it.
Cons:
So, the main plot of this week's episode is dealing with the fallout of the revelation that Hook is a Dark One. We see how in Camelot he is angry at Emma, but Emma tries to convince him that they can defeat the Darkness inside both of them, as long as they work together. Hook seems to trust Emma, and Emma proves her trust in Hook by handing over Excalibur. Then it turns out... nope! Hook has fully succumbed to the Darkness. He decides to enact his own Curse to get back to Storybrooke - that way, he can finally get his long-awaited revenge on Rumple, who is still back there. Emma tries to stop him, but Hook crushes Merlin's heart as a way to enact the curse. This is a loophole - Nimue loves Merlin, so since she is all Dark Ones, it works the same way as Hook crushing the heart of the person he loves. Emma adds in a memory erasure to the Curse, erasing Hook and everybody else's memories of the fact that he's the Dark One. She figures this way Hook won't remember why he enacted the Curse to get back to Storybrooke in the first place, and this will protect him.