My theory is this:
Henry brought Emma to SB. Therefore he fulfilled a part of prophecy, because he has brought Rumple and Bae together indirectly .
But to find his son, Rumple had to leave SB. Now he is injured, because of Hook and it doesn’t look so good for him. Because as you can see in the first 9 minutes, his name disappears on his Dagger. I think this is his “Undoing”.
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"Love is a mystery to be uncovered." - Belle
Keeper of: Belle's Love for Rumple,her Hair and her Eyes,Rumple's Eyes,his Call to Belle and his Dreamcatcher,Snow's Heart, Emma's enjoying Magic,Regina's Castle