The book follows the adventures of young assistant pig-keeper Taran as he goes on a quest to discover his true parentage. Fans of the series will recall that by this point he's finally avowed his love for Princess Eilonwy, and he's necessarily feeling a bit antsy about not knowing his own background. There are two happy results of this: first, it guarantees us a nice meaty quest-narrative, which is always fun, and second, it means a book with no insufferable Eilonwy in it, which can only be accounted a good thing.
Instead, we have Taran (and Yoda-speaking Gurgi) finding their usual tally of adventures, and we have Alexander's passionate, at times sharply good prose describing it all (at one point when Taran is sick, we're told "Fever came, sweeping over him, a blazing forest through which he staggered endlessly"). Taran encounters our old friend King Smoit again and saves his life; Taran fights and as often as not thinks up alternatives to fighting; and in the book's most memorable sequence, Taran confronts the evil wizard Morda (hence the aforementioned pyrotechnics), who has already turned all of Taran's friends into animals and now threatens to do the same to Taran - and not just any animal in his case but the most lowly and wretched of them all, a blind, writing earthworm!
The wizard has scoffed contemptuously at Taran's threats of sword-play - Morda can't be killed, he tells our young hero, because he's used his mystical arts to locate his actual life outside his physical body - and he's hidden it away where nobody would think to look. Earlier in the book, Taran and his friends had by complete accident found a small cask made of bone hidden away, and Taran had kept it. In the thrilling confrontation with the wizard, Taran makes a leap of intuition that turns out to be right (and had the inevitable echoes of Tolkien):
In Taran's mind a strange thought raced. The wizard's life safely hidden? Where none would find it? Taran could not take his eyes from Morda's hand. A little finger. The coffer in the hollow tree. Slowly, terrified lest his hope betray him, Taran thrust a hand into his jacket and drew out the fragment of polished bone.
At the sight of it Morda's face seemed to crumble in decay. His jaw dropped, his lips trembled, and his voice came in a rasping whisper. "What do you hold, pig-keeper? Give it into my hands. Give it, I command you."
"It is a small thing my companions and I found," replied Taran. "How should this have worth to you, Morda? With all your power, do you covet such a trifle?"
A sickly sweat had begun to pearl on the wizard's brow. His features twitched and his voice took on a gentleness all the more horrible coming from his lips. "Bold lad to stand against me," he murmured. "I did no more than test your courage to see if you were worthy to serve me, worthy of rich rewards. You shall have gold in proof of my friendship. And in proof of yours, you shall give me - the small thing, the trifle you hold in your hand ..."
But the real drama of Taran Wanderer is personal, not sorcerous. Taran meets Craddoc, the herder, and spends a long time living in his cabin and on his humble farm, which Alexander describes with his typical broad strokes and bright colors:
The farmstead Taran saw to be a tumbledown cottage, whose walls of stone, delved from the surrounding fields, had partly fallen away. Half-a-dozen ill-shorn sheep grazed over the sparse pasture. A rusted plow, a broken-handled mattock, and a scant number of other implements lay in an open-fronted shed. In the midst of the high summits, hemmed in closely by thorn bush and scrub, the farm stood lorn and desolate, yet clung doggedly to its patch of bare ground like a surviving warrior flinging his last, lone defiance against a pressing ring of enemies.
Craddoc convinces Taran that he is the boy's father, and the seasons Taran and Gurgi spend on Craddoc's farm are perfectly, winsomely rendered. When a terrible snowstorm descends on the hollow and Craddoc suffers a terrible fall from a ledge, many truths are revealed, and Taran is forced to continue on his quest. But the pause that is the essential quality of Taran Wanderer is nevertheless a welcome change of pace from the headlong narratives of the other books. That headlong narrative can be a great thing in itself - I doubt that anybody who's ever read The Black Cauldron has ever forgotten it - but sometimes it's nice to slow down a little and get to know the hero.