Macbeth invites Banquo to dinner at the palace. He then sends a servant to get two murderers. He tells the murderers they have to kill Banquo and his son.
We will kill them both.
Lady Macbeth sends a servant to get Macbeth. He tells her the work they've done is not finished but doesn't tell her what he plans to do.
My mind is full of scorpions.
The murderers wait in a wooded park outside the palace. They kill Banquo, but Fleance gets away in the dark.
A feast is set and guests are there. The murderers tell Macbeth what happened. Macbeth is plagued by a hallucination of Banquo's ghost in his chair. Lady Macbeth sends the confused guests home.
He sometimes has visions.
The three witches meet Hecate, the goddess of witchcraft. She scolds them for telling Macbeth about his future without consulting her. She says when they meet him the next day, they need to give him a false sense of security.
Lennox and another lord discuss what has happened. Even though Fleance is blamed for his fathers death, they think it was Macbeth. They hope that Scotland can be saved from Macbeth's tyranny.