In a review, Liesl Schillinger writes:

In his latest novel, “The Dream of the Celt,” the Peruvian author Mario Vargas Llosa unearths the achievements of [Roger Casement] this complicated man of conscience, reasserting his credentials as “one of the great anticolonial fighters and defenders of human rights and indigenous cultures of his time, and a sacrificed combatant for the emancipation of Ireland.” Although Casement was an Irishman (born in 1864 to a Protestant father and a Roman Catholic mother, and orphaned in childhood), he spent most of the first decade of the 20th century as a British consul, investigating working conditions on rubber plantations in Congo and Peru. His reports, which stirred public outrage, earned him a knighthood in 1911. This honor notwithstanding, Casement’s loathing of colonialism gradually led him to see England as an enemy occupier and turned him into a fervent Irish nationalist. In 1914, in the early months of World War I, Casement traveled to Germany with his perfidious Norwegian lover (a man named Eivind Adler Christensen) to seek the kaiser’s help in arming the Irish against Britain. Upon his return to Ireland, in April 1916, he was captured, imprisoned, stripped of his knighthood and hanged as a traitor in Pentonville Prison in London.