answer
Act 3, scene 1 of Romeo and Juliet begins with Mercutio and Benvolio entering. The scene is set in a public area in Verona. Benvolio is pleading with Mercutio to calm down and go home.
I believe that the adverb phrase is "during the fifteenth century"
A term for a story within a story would be called a frame story.
I hope this helps!
