Casement is an Irish Protestant who serves as a British diplomat during the early part of the 20th century. He wins international acclaim after exposing the illegal practice of slavery in the Congo and parts of South America. Despite his Ulster Protestant roots, he becomes an ardent supporter of the Irish independence movement and, after the outbreak of World War I, travels to the United States and then to Germany to secure aid for an Irish uprising against the British.
Germany, which is at war with Great Britain, promises limited aid, and Casement is transported back to Ireland in a German submarine. On April 21, 1916, just a few days before the outbreak of the Easter Rising in Dublin, he lands in County Kerry and is picked up by British authorities almost immediately. By the end of the month, the Easter Rising has been suppressed and a majority of its leaders executed.
Casement is tried separately because of his illustrious past but nevertheless is found guilty of treason on June 29. On August 3, he is hanged by John Ellis and his assistants at Pentonville Prison in London. Casement is the last to be executed as a result of the Easter Rebellion.