Answer: The error is in "to take the shortcut".
Explanation:
In the sentence "To get to the store, Moria had to cross the street, walk to the corner, and to take the shortcut across the park" we have the preposition "to" after the verb "had". The preposition already refers to each and every element that is mentioned after it, so there is no need to repeat it. It refers to "cross the street", "walk to the corner", and "take the shortcut across the park" as well.
In order to make the sentence grammatically correct, all we have to do is eliminate the preposition "to" that was repeated right before "take the shortcut across the park."
Thus, the correct form is:
To get to the store, Moria had to cross the street, walk to the corner, and take the shortcut across the park.
