This book, "Doctor Who: The Ultimate Evil" by Wally K. Daly, presents a novelization of a previously untelevised BBC series script from 1985. The narrative begins by setting the stage for a cosmic conflict between two technologically distinct planets, Tranquela and Ameliera, within the same solar system. The central plot revolves around a mysterious "hate-wave" weapon that induces murderous rage, impacting the inhabitants of Tranquela and threatening to ignite a war with Ameliera. The Doctor and his companion, Peri, become entangled in this escalating crisis, working with local scientists Ravlos and Kareelya to uncover the weapon's source and the orchestrator of the conflict, the sinister Dwarf Mordant, who manipulates events with the help of the ambitious Escoval. Ultimately, the story details the efforts to neutralize the threat, expose the deception, and restore peace, all while exploring themes of truth, lies, and the inherent capacity for both good and evil within individuals.