In medieval Scotland, a general encounters three witches on a desolate heath while returning from a victorious battle. The witches prophesy that he will become the king of Scotland, igniting his latent ambition. With the prophecy in mind, he writes to his wife, who becomes even more determined than he is to see it fulfilled. His wife persuades him to assassinate the current king during a visit to their castle. Overcome by ambition and spurred by his wife’s fierce resolve, he reluctantly agrees to the grim task.

As the deed is done, the general ascends the throne but quickly descends into paranoia and tyranny. Haunted by guilt and suspicion, he orders the deaths of those he perceives as threats. His wife's own conscience begins to unravel under the weight of their crimes, leading her down a path of madness. The kingdom plunges into chaos as factions rise against the oppressive ruler, setting the stage for inevitable conflict and retribution.