And here the trilogy ends. Spoilers ahead for A Wizard of Earthsea and The Tombs of Atuan.
It opens with a young prince, Arren, coming to the Archmage, the great and famous Sparrowhawk who brought back the Ring of Erreth-Akbe from the tombs -- also known as Ged. But not all is well. They have the Rune of Peace, but where is the king? And Arren tells of how the wizardry is losing power in his father's land. The wizard who should have cast the spell on the lambing could not do it, and Arren's father said it instead, but it had no effect.
The Master Wizards of Roke are disturbed; this is the news coming from all about. So Sparrowhawk sets out to find out what happens, and he takes Arren with him. They find hints and pieces: people who have lost their magic, or their skills, or their love of life, speak of someone who offers immortality.
The end of which is not reached before dealing with a wizard whom Ged knew long ago, a bitter road through mountains, dragons losing their speech, dyers who can no longer produce the colors of before, a slaver, a woman justifying her cloth wares as more honest than wizardry, a madman jumping into the sea in hopes of escaping both life and death, and much more.