This scene is set at the heath, in a thunder storm (for effect..) with the witches and Hecate (the chief witch.) Hecate is grumpy at the witches for not involving him/her (don’t know the gender of Hecate) with their devious deeds regarding Macbeth. Hecate tells the witches to meet with him/her the next morning, so she can also talk to Macbeth (who must have arranged a meeting with the witches by now). Hecate then says he/she is going to force Macbeth even further down his dark path, “He shall spurn fate, scorn death, and bear He hopes ‘bove wisdom, grace and fear: And you all know, security Is mortals’ chiefest enemy.” meaning he/she will make him know fear more than wisdom or grace, and then hints at the end he/she is going to offer Macbeth immortality to mess with him even more…….. then Hecate leaves and the witches hurry to leave.
