I, The King is the story of Philip IV of Spain and of the women who most influenced his life. Among them was his first wife, Isabel of Bourbon, the beautiful child bride who became his wife and respected Regent; his 'true love' Inés Calderón, the charming young actress, who gave him his best-loved son; and Sor María, the Abbess, gifted with mystical powers, of a remote provincial convent, whose correspondence with the King, comprised more than 600 letters and covers a period of more than twenty years.