Latin American fiction: A tragic hero's tale The Dream of the Celt. By Mario Vargas Llosa. Farrar, Straus and Giroux; 404 pages; $27. Faber and Faber; £18.99. IN 1884 Roger Casement, an ascetic young Ulsterman, joined an expedition up the Congo river led by Henry Morton Stanley, believing that commerce, Christianity and colonialism would emancipate the dark continent. When he left Africa 20 years later, Casement was the leading figure in an international campaign to denounce the abuses committed by the Congo's Belgian colonisers. As British consul, he published a report that detailed how the African population were beaten and mutilated to force them to supply rubber for export to Europe. When news reached London that the rubber boom had prompted a similar reign of terror against the indigenous population in Putumayo, in the Peruvian Amazon, the British foreign secretary sent Casement to investigate with the words: "You're a specialist in atrocities. You can't say no. His findings prompted the collapse of the Peruvian Amazon Company, the London-registered firm responsible. Casement was knighted, and the Times hailed him as "a great humanitarian." A passionate man of complex character, Casement is a tailor-made protagonist for Mario Vargas Llosa, a Peruvian writer who won the Nobel prize in literature in 2010. "The Dream of the Celt" is a meticulously researched fictional biography and a clever psychological novel. Casement's fame quickly turned to notoriety. Only a few years after his lauded success in Peru he was hanged in London's Pentonville prison as a traitor. Having transferred his thirst for justice to the fight for Irish independence, he sought German military support for the cause during the first world war. Casement was caught in 1916 on an Irish beach during a foiled attempt to land 20,000 German rifles. His British captors sought to besmirch further his name by circulating diaries in which he detailed homosexual encounters with young men on several continents. The strongest passages in the book are those in which the author skilfully interweaves scenes in Pentonville prison with details of Casement's earlier life to trace the evolution of Casement's consciousness. "The Dream of the Celt" is a moral tale. It is about the choice between denial or denunciation in the face of evil, and the fine line between activism and fanaticism. That makes an old story strikingly contemporary.