In the conclusion of two-part episode that serves as the season three finale, Emma and Hook must find a way to return to Storybrooke, but in their quest to return, they have to find a way not to interfere or tamper with the events that lead up to the first curse, or else they risk altering the entire timeline, and could end up warping the future existence of everyone involved, including Emma, Hook, as well as Emma's family back in present-day Storybrooke.
