In a fairytale, a young woman is brought to a mysterious nobleman's castle to be his bride. But he has to leave for a whole and gives her the keys that will open every room in the estate.
On the condition that she not open one specific door.
That is forbidden.
Curiosity eventually gets the better of the young woman and she eventually opens the door to the forbidden room, wondering what kind of treasure he could be hiding.
Teenage Mutant Ninja Turtles (1990)
We open on some very nice B Roll of NYC (the movie itself was mostly shot in North Carolina) with some exposition from lovely TV Reporter April O'Neil covering an organized crime spree.