Macbeth

Returning from battle, the general Macbeth is hailed by three witches as a future king - a prophecy his wife seizes on with a ruthlessness that outpaces even his own ambition. Their first murder, of the sleeping King Duncan, is meant to end the bloodshed; instead it begins a spiral of paranoia, further killing, and encroaching madness that neither of them survives. Shakespeare's shortest and darkest tragedy, written around 1606, is a masterclass in how guilt corrodes from the inside - and gave the language phrases still quoted, four centuries later, by anyone contemplating an unforgivable act.