Macbeth Act I, Scene vii Summary

Somewhere in the castle Macbeth sits alone, contemplating the murder of King Duncan. Now, pay attention because this part is important.
Macbeth says that if it were simply a matter of killing the king and then moving on without consequences, it wouldn't be a big issue. The problem with murder is what happens afterward – Macbeth would be damned to hell in the afterlife. Macbeth also muses that murdering Duncan in his own home would be a serious violation of hospitality. He's supposed to protect the king, not murder him. Plus, Duncan is a pretty good king (if not a bit "meek") and heaven is bound to frown upon murdering such a good fellow. Things likely wouldn't go Macbeth's way come judgment day. Probably not a good idea to commit murder. Macbeth realizes he has no justifiable cause to kill the king and he admits that he's merely ambitious.
In the midst of his doubt, Lady Macbeth enters.
Macbeth announces "we will proceed no further in this business," meaning the murder plot is off.
Lady Macbeth gives him a tongue-lashing, questions his manhood, and lays out the plan to get Duncan's guards drunk and frame them with the murder. She insists that Macbeth keep his promise to kill the King. She claims she'd tear a nursing child from her breast and "dash" its "brains out" if she had promised to do it. Therefore, if Macbeth can't keep his vow, then he isn't a man.
Macbeth commends her for her strength (enough for the both of them, it seems) and he finally resolves to go through with the murder.

Act II, Scene i

Act I, Scene vi