in grave danger, very likely from the evil sorceress Achren, from whom Taran and Eilonwy escaped in The Book of Three. Taran and Gwydion witness Chief Steward Magg leave the castle at night to signal a ship at sea. The next morning, Magg and Eilonwy do not show for breakfast and it is concluded that Magg has kidnapped the princess. King Rhuddlum organizes search parties, with Prince Rhun in charge of one. The king assigns Taran to the same group and personally asks him to protect his son Rhun during the search, confiding to Taran that he and Queen Teleria hope to betroth their son to Eilonwy. Although resentful and envious, Taran vows to ensure Rhun's safety. Shortly before dusk, Rhun separates from the group. Taran, Fflewddur, and Gurgi pursue, and the next morning they find Rhun at an abandoned hut in the woods. Inside, they find a small book of blank pages that Rhun keeps for himself, along with a sheaf of notes belonging to the former resident, Glew, a man who experimented with size-enhancement potions. As the companions prepare to leave, they come face to face with Llyan, a mountain cat that Glew made larger than a horse, seemingly intending to eat them. Fflewddur entrances the cat with his harp playing, allowing the companions to escape. Taran's pet crow Kaw spots Magg and Eilonwy heading for the river Alaw on horseback. Reaching the river, Rhun finds Eilonwy's bauble and tracks indicating Magg and Eilonwy continued their journey by boat. The companions hastily construct a raft to follow downstream, but it disintegrates before reaching the mouth of the river. While repairing the raft, Rhun tumbles into a deep pit and causes a landslide that traps the group. Exploring nearby caverns, the companions eventually find Glew, who is now a giant trapped in the caverns by his enhanced size. The companions promise him Dallben's aid in creating an antidote to his potion, while Glew promises to lead them out of the caverns. Instead, Glew takes the companions to a dead-end and traps them. Glew explains he already knows how to make an antidote that will decrease his size, but he must kill one of the companions for a final ingredient. Glew leaves, promising to free the others if one of them agrees to be a sacrifice for his antidote. Rhun surprises everyone by volunteering to sacrifice himself, believing he is