Macbeth Act II, Scene iii Summary

Now that Shakespeare's given us a murder and a lot of spooky crazy talk from Macbeth, it's now time for a brief, comedic interlude. There's a ton of knocking and the Porter (the guy who's supposed to answer the door) does a lot of joking around about what it would be like to be a porter of "hellgate." Apparently, a porter in hell would be a busy guy since there are so many evil and corrupt people in the world.
The Porter says maybe there's an "equivocator" at the door.
Note: An "equivocator" is a person who speaks ambiguously or doesn't tell the whole truth. This is likely an allusion to the treatise written by the Jesuit Henry Garnet, who encouraged Catholics to speak ambiguously or, "equivocate" when they were being questioned by Protestant inquisitors (so they wouldn't be persecuted for their religious beliefs). It's also significant that Henry Garnet was tried and executed for his role in the Gunpowder Plot of 1605, when a group of Catholics planned to blow up the King and Parliament (they stored kegs of gunpowder in a nearby building). The plot failed but it was a deeply disturbing and shocking event that resonates in this play, especially where we've just witnessed Macbeth returning from the room where he has murdered the sleeping king.
Then the Porter says, no wait, this castle's way too cold to be hell but, gee, who could possibly be at the door at this hour.
It's Macduff and Lennox at the door – the two noblemen have come to fetch the king.
The Porter makes a bunch of jokes about how drinking an excessive amount of alcohol, (which he's been doing all night), makes a man frisky but it also detracts from his "performance" in the sack. It also turns his nose red, makes him have to urinate.
Enter Macbeth, the picture of sleepy innocence while he makes small talk with Lennox and sends Macduff to wake Duncan.
Lennox notes that some spooky things have been happening all night – he heard a bunch of screams, there was a little earthquake, and the fire in his chimney blew out.
Macbeth says yeah, it's been a pretty "rough night."
Macduff reenters, disheveled at finding the King murdered. He raises a fuss as he sends in Lennox and Macbeth to go look at the dead King.
Lady Macbeth and then Banquo hear the news after waking up to the commotion. Macbeth, Lennox, and Ross come back after looking at the King's body.
Macbeth takes the time to begin a way-too-eager eulogy about the King's great virtues.
Malcolm and Donalbain, the King's sons, are the last to wake up and hear the news that their father has been murdered, to which Malcolm replies, "O, by whom?"
Lennox says the drunken guards covered in the King's blood and holding their daggers are a good bet.
Macbeth casually announces that he killed both of the guards in a fit of pious rage, out of his love for the King. No one thinks it's weird that the guards went to sleep with the bloody daggers in hand.
Lady Macbeth, upon hearing that Macbeth has done this, needs to be escorted out (this was not part of her plan).
Donalbain and Malcolm privately decide that they probably shouldn't stay in the house where their dad was killed. Good thinking. Malcolm will go to England and Donalbain to Ireland, making it more difficult to murder them both.
The dead king's sons slip out, unnoticed.
Meanwhile, everyone else agrees to get dressed and then talk about how they're going to respond to the King's death.

Act II, Scene iv

Act II, Scene ii