King Lear, the aging King of Britain, determines to split his kingdom evenly between his three daughters: Goneril, Regan, and the young Cordelia. Goneril, when asked, gushes her protestations of love for her father; Regan follows with even more flattery. Cordelia, however, is sincere in her love of Lear, and she declines to pander to him—she simply says she loves him the way a daughter should love her father. Lear is put off by this lack of pomp and disinherits her, although the King of France says that he would be proud to marry her. When one of his lords, Kent, tries to reason with him, Lear banishes him from the kingdom. Gloucester, another of Lear’s lords, has two sons, Edgar and Edmund. Edmund is Gloucester's bastard, and intends to gain his father's inheritance by tricking him into thinking that Edgar is plotting to murder him. Edgar disguises himself as a madman and goes into hiding.
Lear is soon to find out how much love Goneril and Regan actually have for him. Both daughters treat him miserably when he stays with them, and Lear is transformed from a powerful king to an impotent old man with only Kent (who has disguised himself and disobeyed Lear's decree of banishment) and a Fool to accompany him. In the middle of the play, Lear is driven mad by his grief at seeing the true nature of his daughters. On a lonely heath, he rages at a storm. There they encounter Edgar, in his disguise as Tom o' Bedlam. Gloucester helps them, providing shelter and sending them to Dover to meet Cordelia and the French king, who has landed an army in England to come to Lear's aid. But Gloucester is betrayed by Edmund and has his eyes put out.
In his poor, blind state, Gloucester encounters Edgar (still disguised). Edgar does not yet reveal himself but leads his father toward Dover. In the meantime, Albany, husband of Goneril, has voiced his displeasure at the treatment of Lear and Gloucester. With Regan becoming a widow, and Goneril seeing her husband as a coward, both women turn their attentions to Edmund as a prospective love interest. While this intrigue is going on, the English and French armies meet on the battlefield; the English win the day. When Lear and Cordelia are taken captive, Edmund gives an order that they be hanged. Edgar encounters Edmund, and the two duel, with Edgar giving Edmund a mortal wound. Word also comes that Regan and Goneril are dead; Goneril poisoned Regan to win Edmund from her, and then killed herself upon Edmund's defeat. Knowing he is about to die, Edmund repents and reveals his plots—including the impending deaths of Lear and Cordelia.
Lear enters, bearing Cordelia's body. Overcome by his sorrow, Lear collapses and dies beside his lone, loving daughter. Gloucester is dead as well, having been reconciled at the last with Edgar. Kent and Edgar depart, leaving Albany to rule Britain.