The second volume continues to the meeting with Théoden king of Rohan, and includes the invention and evolution of Lothlórien and Galadriel; plans for Frodo and Sam's progress to Mordor; the creation and development of Treebeard, the Ents, and Fangorn; discussions of the original map of Middle-earth at the end of the Third Age; and the evolution of Cirth in an appendix.

It includes The Notion Club Papers (a time-travel story related to Númenor), a draft of the Drowning of Anadûnê (that led to Akallabêth), and the only extant account of Tolkien's constructed language Adûnaic.

Some paperback editions of the fourth volume, retitled The End of the Third Age, include only the materials that relate to The Lord of the Rings.

As Christopher Tolkien noted of the first two volumes, his father had eventually brought the story up to Rivendell, but still "without any clear conception of what lay before him".

[T 5] Thereafter Tolkien's problem was rather one of selecting between alternative accounts, so as to produce the best effect – two episodes in the "fascinating study"[2] Sauron Defeated that were eventually deleted being the pardoning of Saruman, and an awards ceremony at the book's close.