When Lady Macbeth learns that Macbeth might become king, she makes a commitment to support him in any way she can. A spine-chilling plan is hatched to assassinate King Duncan when he pays a visit due to the wish of both husband and wife for Macbeth to become king.
King Duncan is killed by Macbeth while everyone is sleeping and the guards are drunk. When the murder is discovered, Lady Macbeth leaves the bloody knives next to the victim's body, and Malcolm and Donalbain escape the kingdom out of fear for their safety. They are held accountable for killing the King.
With the murder, Macbeth felt terrible guilt. After being crowned king of Scotland, he plans the murder of Banquo and his son. However, he learns that Fleance, Banquo's son, managed to flee the scene of the crime. He behaves strangely at the meal in remembrance of Banquo because he sees the ghost of Banquo, and despite his wife's best efforts to calm him down, he continues to worry and act strangely.
Lady Macbeth ends up killing herself due to all the guilt of having been part of the murders of not just King Duncan but many others aswell.