Enter Ghost and Hamlet:
Hamlet has gone as far as his courage will take him, and says, "Wither wilt thou lead me? Speak, I'll go no further" (1.5.1). The Ghost does speak, and he demands that Hamlet "mark" him--not just listen, but pay attention. He tells Hamlet he is "thy father's spirit," and must soon return to the prison of purgatory and its flames. Finally, he gives Hamlet a command: "If thou didst ever thy dear father love . . . / Revenge his foul and most unnatural murder" (1.5.23-25). Hamlet promises that he will "sweep to [his] revenge," and the Ghost replies, "duller shouldst thou be than the fat weed / That roots itself in ease on Lethe wharf, / Wouldst not stir in this" (1.5.32-34).
Thus the Ghost, who is all that inspires respect--warrior, king, and father--promises Hamlet a burden of shame and guilt if he does not revenge him.
Only after this terrible introduction, does the Ghost deliver the news: Claudius, now king, killed Hamlet's father. "O my prophetic soul!" (1.5.40) says Hamlet. It's what he expected. But then the Ghost turns to something that has been on Hamlet's mind even more than the death of his father--his mother. The Ghost says that Claudius "won to his shameful lust / The will of my most seeming virtuous queen" (1.5.45-46). (We'd like to know whether that happened before or after Old Hamlet died. And we'd like to know whether the queen was an accessory to murder. But neither of those questions is answered here, or elsewhere in the play.) The Ghost now proceeds to denounce his queen in most bitter terms. She left his bed to "prey on garbage" (1.5.57).
Finally the Ghost gives the details of the murder. While Old Hamlet was taking a nap in his orchard, Claudius poured poison in his ear; the poison curdled his blood and rose to his skin, until his body was covered with a "vile and loathsome crust" (1.5.72). So Old Hamlet had his life, his crown and his queen stolen from him all at once. Worse, he died without a chance to pray or take the last rites, so that now, instead of being in heaven, he is burning in the fires of purgatory.
It is all "O, horrible! O, horrible! most horrible!" (1.5.80), but now it's now almost morning and the Ghost must leave. His parting words have an unexpected twist:
If thou hast nature in thee, bear it not;So Hamlet is supposed to hate the fact that his mother is having sex with King Claudius, and he is supposed to kill the King to put a stop to it, but he is not supposed to do a thing to his mother, or even think bad thoughts about her.
First, Hamlet exclaims "O all you host of heaven! O earth! what else? / And shall I couple hell?" (1.5.92-93), as though he is thinking of what to swear by. Shall he swear by God and all the angels of heaven? By earth? Or maybe he should swear by hell, in case the Ghost came from there. This thought makes him say "O fie" to himself, but he feels weak, overwhelmed, and asks his heart to stay young and his sinews to stay strong.
Now he promises to remember the Ghost, and only the Ghost, saying, "Yes, by heaven!" But immediately afterwards he disobeys the Ghost's command to "taint not thy mind" against his mother, and exclaims "O most pernicious woman!" (1.5.105) The thought of his mother brings with it the thought of his step-father, and Hamlet cries out "O villain, villain, smiling, damned villain!" (1.5.106). He even takes out a notebook ("my tables") to write note the fact that "one may smile . . . and be a villain."
Enter Horatio and Marcellus:
Horatio sensibly comments that "There needs no ghost, my lord, come from the grave / To tell us this." Then, after some more rigmarole from Hamlet, Horatio says "These are but wild and whirling words, my lord" (1.5.133). Horatio seems to be right. Hamlet has promised to take revenge upon the King, which will probably be a dangerous undertaking, and therefore he has a need for secrecy, but he has no obvious reason to distrust either Horatio or Marcellus. And as a matter of fact, Hamlet later tells Horatio the Ghost's message; we know this because just before the play-within-the-play Hamlet tells Horatio that one scene of the performance "comes near the circumstance / Which I have told thee of my father's death" (3.2.76-77). But right now, Hamlet is not only refusing to tell what the Ghost told him, he mocks Horatio's questions, saying "For your desire to know what is between us, / O'ermaster't as you may" (1.5.139-140).
Ghost cries under the stage:
What follows is manic. Hamlet welcomes the Ghost's assistance with a kind of joy, referring to him as "truepenny" and "old mole." All the while, Horatio and Marcellus are shifting about the stage because the Ghost has spooked them, and Hamlet is becoming ever more insistent, demanding that they never give the slightest indication that they know anything, not with so much as a nod of the head, even if Hamlet acts strange. He might, he says, "think meet / To put an antic disposition on" (1.5.171-172). This is something that Shakespeare's audience would not have found peculiar. Many of them would have seen or heard of at least one other play in which a revenger acted crazy in order to lull his enemies into a false sense of security. But Horatio and Marcellus must be totally confused, seeing that they still don't know anything about any murder or revenge.
Finally, Hamlet stops, saying to the Ghost "rest, rest, perturbed spirit." Most editors assume that the men swear by putting their hands on Hamlet's sword, and editors generally put in a stage direction such as "They swear," but there's no such stage direction in any of the original texts.
After all of this, Hamlet's high spirits seem to take a plunge. He again asks the men to keep his secret and invites them to go with him back down into the castle, but says "The time is out of joint--O cursed spite, / That ever I was born to set it right" (1.5.188-189).