Blood appears frequently throughout the play: on the dagger soaked in blood, the bloodstained hands, or the blood smeared on the face of the murderer. In each case, the blood appears when it has been or is about to be unjustly spilled in an act of violence that contravenes fundamental moral principles. In the play, the sight of blood underscores the extent to which the boundaries of acceptable moral behavior have been contravened.

Even more important than tangible blood is blood that is hallucinated by guilty characters. After Duncan’s murder, Macbeth and Lady Macbeth begin to imagine blood everywhere. They cannot wash it away because this blood is a psychological manifestation of their shame. In the play, wrongdoing causes madness, loosening the characters’ grip on reality.

But also represents legacy. Duncan’s son Malcolm is his ‘blood’, just as Fleance is the continuation of Banquo’s bloodline, which is set to inherit the throne (which is what happened to the historical figure Fleance is based on). Macbeth and Lady Macbeth, however, have no heirs and no bloodline to leave behind. The only legacy they leave is the blood they have spilled rather than the blood that they have helped to create.