King Lear is one of Shakespeare’s four great tragedies. The story follows an aging king, Lear, who decides to step down from the throne. Before doing so, he asks his three daughters to publicly declare their love for him—planning to divide his power and kingdom based on how convincingly they express their affection.

The eldest and second daughters flatter him with grand, exaggerated declarations, swearing they love him more than anything else in the world. Pleased, Lear turns to his youngest daughter, Cordelia, who speaks with sincerity:
“I love you as a daughter ought to love her father—no more, no less.”

Lear is furious. He says to her, “Fix your words, or you’ll lose everything.” But Cordelia remains unyielding:
“You are my father. You loved me and raised me, and I will fulfill my duty to love, honor, and care for you. But I cannot promise to love you more than anyone else. When I marry, I will share my heart with my husband and love him with half of it, as a wife should. If I love only you, as my sisters claim to love you, then what’s the point of getting married?”

Enraged, Lear disowns Cordelia and divides his entire kingdom between her two sisters.

Cordelia is married off to the King of France and leaves her homeland.

You can probably guess how the rest of the story unfolds:
The elder daughters turn against their father, mistreating him terribly. Cordelia returns with the French army to rescue him. In their reunion, Lear is full of guilt; Cordelia forgives him. But tragically, she is defeated and executed.
The two older sisters become bitter enemies, manipulating and betraying each other until both die. Lear dies in utter grief and despair.
As is often the case in Shakespearean tragedy, almost no one makes it out alive.
(Of course, the original play is far more intricate, but this is the core storyline.)