Of course, as we learned this week, prophecies are far from clear in the OUAT world. So what does Henry being Rumple's undoing actually mean? We're sure the answer will unfold over time on the show, but we can't help but speculate about the many ways this plotline could go from here.
Here are our first thoughts on what the seer's words could mean.
Henry will kill Rumple. The straightforward reading of the prophecy is that Henry will somehow be responsible for Rumple's death or destruction. However, we doubt things will play out so simply. After all, "undoing" is a very vague word that could mean a lot of things, and we bet the writers did that on purpose. (Though, as a side note: If Henry did kill Rumple, would he then become the Dark One? Because that would be quite a shock.)
Another ironic loop. During "Manhatten" we learned that the seer foretold that Rumple's actions in the Ogre War would leave Bae fatherless. Which they did, in a very roundabout way, after Rumple's cowardice left Bae stranded in another world. It's possible that a similar thing will happen here. If Rumple does go all Big Bad and tries to kill Henry, he will almost certainly lose the two people he loves: Bae and Belle. His attempt to kill Henry would therefore make Henry his undoing.
The undoing of the Dark One. On the other hand, we don't have to read this prophecy as a bad thing. Maybe when the seer said Henry would be "your" undoing she meant Rumplestiltskin the Dark One, not Rumplestiltskin the man. Perhaps his growing love for his grandson — which could manifest in the decision not to kill Henry, or perhaps even to save his life somehow — will be what ultimately saves Rumple from the Dark One curse.
What do you think this prophecy will mean for Rumple and Henry? Share your theories in the comments below!