The following are some suggestions. You can find a thorough discussion of this play in the eNotes study guide and other materials.
Macbeth begins thinking about murdering King Duncan because of what the witches told him about becoming king.
Macbeth discusses murdering the King with Lady Macbeth, who encourages him to do so that very night.
Macbeth tries to get Banquo to join in his plot against Duncan.
Macbeth actually murders Duncan.
Macbeth has Banquo murdered because he is afraid of him--especially since the witches have prophesied that Banquo's heirs will be kings. He thinks Banquo knows he killed Duncan and might inform on him. He suspects that Banquo might kill him in order to make sure his sons would become kings.
Duncan's son Malcolm has fled to England and is raising an army to invade Scotland and unseat Macbeth.
Scotland is in chaos because of Macbeth's incompetent and despotic rule. See opening of Scene 3.
Macbeth has Macduff's wife and children murdered to punish Macduff for deserting him and to set an example to discourage further desertions.
Lady Macbeth, who helped her husband kill Duncan, seems to be losing her mind due to guilt. She dies, probably a suicide.
The English army reinforced with Scottish deserters overthrow Macbeth's weakened army.
Macbeth is killed by Macduff.