Macbeth Act I, Scene iii Summary

The three witches meet again on the heath and check in about what everyone's been up to. The usual witchy stuff: one was killing swine; another recently asked a sailor's wife for her chestnuts. The sailor's wife told the lady to scram so the witches are going to punish the stingy chestnut hoarder by stirring up a little trouble (a storm with some crazy winds) for her husband's ship, which is currently at sea.
The weird sisters are also going to torment the poor guy by depriving him of sleep and by "drain[ing] him dry as hay," which means the sailor's going to have some serious gastro-intestinal problems and/or that he's going to be unable to father children. (In the 16th and 17th centuries, it was common for people to believe in the existence of witches. It was also pretty common for people to believe that witches were in the habit of doing things like whipping up nasty storms and causing male impotence.)
History Snack: as we know, Shakespeare wrote Macbeth during the reign of King James I of England (a.k.a. King James VI of Scotland), who was really interested in witchcraft – he authorized the torture of witches in Scotland in 1591 and also wrote a book on the subject, Daemonologie, in 1603. What started King James's witch-hunting craze? Historians note that it began in 1589, when James's betrothed, Anne of Denmark, sailed to Scotland for the wedding ceremony, the ship encountered a major storm and was forced to take refuge in Norway. James ended up traveling to Oslo, where the wedding took place. On his voyage back to Scotland with his new bride, James's ship encountered another crazy storm, which was blamed on witches. Later, six Danish women confessed to causing the storms that upset James's wedding.
Witch #1, of chestnutty fame, also has a pilot's thumb, a convenient rhyme for "Macbeth doth come," heralded by "a drum."
Hearing Macbeth's approach, the witches dance around in a circle to "wind up" a "charm."
Macbeth and Banquo show up, and Macbeth delivers his first line: "So foul and fair a day I have not seen." Hmm. Where have we heard that line before?
Banquo notices the witches (they're kind of hard to miss) and speaks to them, noting they are unlike the earth's inhabitants, yet are on the earth.
The witches put their fingers to their lips, which does not deter the perceptive Banquo from noticing their beards.
Only when Macbeth tells them to speak do the witches call out. They hail Macbeth as Thane of Glamis, Thane of Cawdor, and future King.
Macbeth doesn't respond immediately. Banquo, who apparently took over the narration for these five lines, mentions that Macbeth is "rapt," as if he's in a trance. (Get your highlighter out – this word comes up a lot in the play.)
Banquo asks if the witches will look into his future too. The sisters cryptically say he will be lesser and greater than Macbeth, and not too happy, but happier than Macbeth. And they say he will be father to kings, though he will not be a king himself.
Macbeth says he's already the Thane of Glamis but it's hard to imagine becoming Thane of Cawdor, especially because the current Thane of Cawdor is alive. He demands to know where the witches got their information
The witches don't respond, but simply vanish into the foggy, filthy air.
Banquo suggests that maybe they're tripping on some "insane root" but conversation quickly moves on to the big news about their own fates, as promised by the witches.
Ross and Angus, two noblemen sent by Duncan (the King), break up the party.
Ross passes on that the King is pleased with Macbeth's battle successes of the day, and announces that the King would like to see him, and also that Macbeth is the new Thane of Cawdor.
Macbeth does some private ruminating. If the sisters' first prophesy that Macbeth will be named Thane of Cawdor can't be evil if it's turned out to be true. On the other hand, the witch's prophesy could be evil, especially since it's got Macbeth thinking about something naughty.
This is where we get the first inkling that Macbeth might be down for a little tyrannicide (fancy word for killing a king). He says he's just had a really awful and disgusting thought about "murder." These "horrible imaginings" make his hair stand on end and his heart beat really fast – he's also feeling as though his mind has been divided.
While Macbeth is deep in thought, Banquo comments to Ross and Angus that Macbeth seems "rapt," in a trancelike state.
Macbeth concludes his dramatic musings and says that he's just going to leave things to "chance." If "chance" wants him to be king, then he doesn't have to lift a finger (against the current king) to make it happen.
They hasten to the King, and Macbeth and Banquo agree to talk more about everything later.

Act I, Scene iv

Act I, Scene ii