Act 1. Scene 4
Marcellus "Lets's follow. 'Tis not fit thus to obey him."
This quote tells me that Marcellus is a good protecting friend to both Hamlet and Horotio. Even if it means not to obey his prince/friend he would do whatever inorder to protect hamlet.
Do you think Marcellus is doing the right thing by protecting Hamlet and not letting him face the facts himself?
Do you think Hamlet would the same for Marcellus?
