Answer:
After saying "You shall not go, my lord," Marcellus steps in front of Hamlet and tries to tell him, to stop him from moving forward. Seeing that Marcellus was unable to stop Hamlet, Horatio joins him and together they try to prevent Hamlet from following the ghost, but Hamlet manages to break free and pursue his goal of following the ghost.
Explanation:
These facts happen in Act 5 and Scene 5 of Hamlet. When Hamlet meets his father's ghost and finds out that his father was murdered by Claudius. Hamlet is alone at that moment, but he is very shaken by everything he heard. When Marcellus and Horatio find Hamlet, the ghost disappears and they don't understand why Hamlet was so upset.
Hamlet explains what happened and says he will follow the ghost, as he needs more answers. Marcellus and Horatio think he is going crazy and try to stop him from moving forward, but without success, since Hamlet manages to break free and suck the ghost.
