Act I, scene iv: Duncan's throne room.
Young Malcolm, who is probably around your age (17, 18) recounts the execution of the traitorous Thane of Cawdor. He says that he died better than he ever lived, and was really apologetic about that whole treason thing. Duncan disingenuously says, "Man, I trusted that guy," two seconds before saying, "Hey! Macbeth!" This is also what we call foreshadowing. Pay attention, peeps--Shakespeare does nothing by accident. (Well, not nothing. Pirates in Hamlet, a rabid bear in A Winter's Tale, and two murderers becoming three murderers in this play all prove otherwise.)
Banquo and Macbeth are congratulated for their battle-awesomeness right before Duncan drops a bomb that (phrase that means "tinkles off") every grown man in the room: He is disrupting the law of tanistry and naming his son, Malcolm, as next in line for the throne. Everyone acts like they are happy, but they are p-mad. Duncan then announces, with utter stupidity/obliviousness that he is going to spend the night at Chez Macbeth. Macbeth promises to ride ahead and let his wife know to lay out the Royal Jammies and prepare for Duncan's most awesome visit, and there is much rejoicing. At least publicly.
Act I, scene v--Macbeth's castle as Inverness, where things get interesting
Lady Macbeth, a.k.a. Grauch Macbeth, is reading a letter, inspiring oh-no-she-didn'ts from the entire Renaissance audience. A chick who can read? A person who can read in 1050 Scotland, where literacy was a major life goal? Wow. Something wicky is afoot. Not only is she reading, the content of what she's reading is really surprising. Most marriages in this time period were arranged, and involved a dominant male figure telling his woman to make him some pie or iron his kilt or go birth a baby or something. Here, Macbeth calls her "my dearest partner in greatness" and confides military and witchy secrets to her. Even more awesome is what the letter doesn't say, but that she totally gets: Duncan will die. She either has a secret decoder ring or she got his psychic fax; they are on the same psychotic wavelength. She flings the letter aside and demands that the ministers of darkness "unsex" her--transform her into a dude. (Think about this for a second: Lady Macbeth would have been played by a male in Shakespeare's day, so a male actor playing a female role would be asking to be a male. Isn't that interesting?)
She wants to be bold, bloody, and resolute--because she fears her husband's kindness. Let' s think about this for a minute, too. This is the husband who gutted a man on the battlefield, who instantly began fantasizing about whacking his boss and kinsman under his own roof in violation of the unspoken, but eternally binding, laws of hospitality. And she thinks he's too nice. What does she want him to do, drown a bunch of puppies for fun? More importantly, what does this tell us about her? Goodness.
A messenger comes and says that Duncan is coming tonight. She gasps, unprepared for Murder Most Immediate, but starts preparing herself emotionally for the plot that must now unfold. Then, her husband comes in the room, and she lustily greets him and they talk chillingly of the future. She tells him to fake kindness to his lord, and that she will take care of everything. He tells her they need to speak more about this plan. She assures him it's all good.
The scene ends with a definitive, palpable sense of fear hovering in the air. Who ARE these freaky wombats?
Act I, scene vi: Macbeth's castle, just outside in the courtyard
In this largely stupid scene, Duncan and Banquo talk about how pretty Macbeth's castle is. Little do they know that this "heavenly seat" will, within hours, be transformed into hell. Lady Mac makes an appearance and sucks up to her king. Little does he know what's in her poisonous mind and heart. We'd feel worse for Duncan if he weren't so blind. He is like the character in the horror film who can't hear the soundtrack with the screeching violins who says, "Hey! All of my friends have been murdered! I think I'll take a bath!"
Bye, Duncan. Soon.
Act I, scene vii: Elsewhere in Castle Inverness: Where Things Get Truly Bizarre (Note: This scene is definitely rated PG-13)
In his first major soliloquy (thinking aloud on stage, since plays don't have subtitles, and a character standing in pensive thought is just boring and pointless) Macbeth decides not to kill Duncan. He just can't do it--Duncan is a nice guy, after all, and he wants to enjoy his newest title for a bit. And we get the idea that he is creeped out by the concept of killing a kinsman and a guest. Macbeth isn't totally bad; he is the Diet Coke of Evil, gone a bit flat from the excesses of battle.
But then his wife comes in, the Triple Espresso of Evil, and the taunting begins. He tells her "We shall proceed no further in this business," and she immediately launches into an epic attack on his manhood. (Not literally--that's not appropriate for the kids!) "You're not a man," she counters, and he's like, "Yo, woman, shut up, I am too," and she's like, "No, you're not," and it's almost as delicious as that toga-ripping sequence in Julius Caesar with all the durst-ing. ("You durst not!" "I durst!" "I dursted more!")
Then she pulls out the Ultimate Scary Weapon of Words, when she says, essentially, "I have breast-fed a baby and know how awesome it is, but if I had promised you, I would rip that kid right off my ___ and dash its brains out."
Now, who on earth says something like this?
And even more surprisingly--he doesn't even blink. His only response to her is, "What if our plan doesn't work?"
She tells him to "screw thy courage to the sticking-place" (referring to a notch on a crossbow) "and we'll not fail." In amazement, he tells her to have male babies only, since females might die inside of her due to her evil ways. She takes this as a compliment (!) and relates her fell plan: Get Duncan's guards drunk, stab Duncan in his sleep, then leave the bloody weapons with the guards. When the body is discovered, cry a lot. Can't go wrong.
Never mind that even in pre-CSI Scotland this is the lamest plan ever ("What? In OUR HOUSE?" she will later cry, which is so believable) the fact that these two are this eager to get all stabby doesn't bode well for a happy ending here.
Duncan, you have minutes to live. Thus endeth Act I.