Laertes is giving his sister Ophelia advice about Hamlet and how not go after him. Then their father Polonius walks in and gives his blessing to Laertes to go off for his school. After Laertes talks to Ophelia and tells her to watch out with Hamlet.
After the guards had seen the ghost they wait another cold night for the ghost to appear. The ghost then appears and beckons Hamlet but the guards hold Hamlet back as they believe that it might bring " airs from heaven or blasts from hell" but Hamlet then breaks free.
The ghost tells Hamlet that he is his father and that he was murdered by King Claudius and that Hamlet should avenge him. Hamlet then swears he will and the ghost tells Hamlet not to be mad at her mother as she didn't know and to let God judge her.