Hamlet, Horatio and Marcellus wait for the appearance of the ghost. The ghost appears, beckoning Hamlet to follow it. Horatio and Marcellus try to restrain him but he obeys the ghost's call.
The Ghost led Hamlet to a remote place on the castle walls. There, Hamlet learns that Claudius murdered his father. The Ghost expects Hamlet to avenge that crime. Hamlet promises to dedicate himself to this solemn duty.
Hamlet refuses to tell Horatio and Marcellus what happened during his encounter with the ghost. Ghost joins Hamlet in demanding silence from Horatio and Marcellus. He forces them to take an oath to never reveal what they have seen and never to comment if they notice anything off about his behaviour in the future.