The central theme of the novel "A Celtic Dream" revolves around denouncing and exposing the exploitation of humans in the Congo forests, once privately owned by King Leopold II of Belgium, and in the Peruvian Amazon, a source of British exploitation until the beginning of the twentieth century. Through his many travels, the Irish adventurer and revolutionary Roger Vargas Llosa (1864–1916), who published the famous report on Africa that bears his name, reveals the extent of social injustice and the dangerous repercussions of colonialism, which he also witnessed in his homeland. Based on his dream of a world free of colonialism and colonies, a dream that would later lead him to wage his own battle: the exploitation of his homeland, Ireland. These two themes would shape the path of this committed and honest man, whose humanitarian work quickly became a reference, while his political work led to a tragic death. In this novel, Vargas Llosa revives a fascinating, historical character, bringing him alive in his own time. At the same time, it invites us to reflect on contemporary themes such as nationalism, misanthropy, and the horrors of European colonialism in Africa and Latin America.