Macbeth believes what the witches have told him supposes his immortality. Since he has killed Banquo (his henchmen have), he doesn’t fear the image of the succession of Banquo descendants as kings. He forgets or subconsciously ignores the fact that Fleance survived because he thinks this image of Banquo kings is a trick played by Banquo’s ghost. Also, Macbeth is now preoccupied the witches’ first apparition who told him to beware Macduff. Since the second apparition tells him he would not be killed of anyone ‘woman-born’ and the third apparition tells him that he (Macbeth) will never be vanquished until the Great Birnam Forest comes to Dunsinane, he believes his is unstoppable. By these last two premonitions, Macbeth thinks he is immortal. But just to be on the safe side, and to heed the warning of the first apparition, Macbeth decides to kill Macduff and his entire family. This is the intended bloody action.