Complex sentence: Back at Mr. Gold's shop, Cora makes it to the weakened Mr. Gold and is about to kill him with the dagger when Regina appears and inserts the cursed heart back into Cora.
Split into simpler sentences: Back at Mr. Gold's shop, Cora makes it to the weakened Mr. Gold. Cora is about to kill him with the dagger when Regina appears and inserts the cursed heart back into Cora.