ROSS: Because they were the murderers - so says Macbeth. LENNOX: And then Banquo is killed and his son Fleance runs away. ROSS: And Macbeth says Fleance was the killer. FX: A door in the castle ...

Banquo was his best friend, and Macbeth has ordered him to be killed. He needed both Banquo and Fleance dead, but Fleance has escaped. This throws Macbeth into a panic. Macbeth is acting secretly.