1. Act 1, scene 2
In this scene, Hamlet is left alone in the room after a celebration for the marriage of his mother and his uncle. He starts a very long epiphany in which he communicates his disgust for the happiness of the kingdom of Denmark despite the great sadness that has been placed upon himself and the country due to his father's death. He feels that his father deserved more, as if to say that his father is important and that the kingdom should honor his memory accordingly and respectively before moving on and celebrating a new, ironic, and disrespectful conjoining of marriage.
2. Act 1, scene 3
In this scene, Polonius and Laertes, Ophelia's brother and father, are instructing her to not associate with Hamlet. When she protests they continue to try convince her that she should not affiliate with him, and in the end despite her efforts to persuade them otherwise, forbid her from associate with him, claiming that he isn't good enough for her. This begs the question of why the father and brother should care, because Hamlet is the prince, and should be good enough, if not better, than her. This also proposes the idea that because of their strange accusations about Hamlet, that they must know something that Ophelia and many others do not know.
3. Act 1, scene 5
In this scene, Hamlet finally encounters the "ghost." It is in this scene that he discovers that the "ghost" is his father. Once he figures this out, his father's ghost continues to tell Hamlet that he was murdered, and that the person who murdered him is his uncle, and his mother's new husband. At this new bit of information Hamlet is shocked and is filled with a new emotion: revenge. However, Hamlet keeps his composure with the new information in order to think clearly and to keep it to himself so that he does not act irrationaly. By discovering that the ghost is his father, and by learning that his father was murdered, Hamlet is no longer depressed, but is now filled with revenge, and wants to bring justice to his father's death.