Lieutenant Arnaud was a Belgian military officer in East Africa, under the command of Colonel Mathieu. In December 1916, Arnaud was assigned to be one of five white officers leading the expedition across from the Belgian camp in German East Africa to Cape Lopez to pick up a shipment of machine guns, mortars and howitzers needed for the taking of Tabora.
Under the leadership of Major Boucher and Captain Henri Defense (Indiana Jones), he survived the overland journey across the Congo without taking ill. However, once aboar the riverboat Collette, he eventually succumbed to disease. After Boucher and Sgt. Barthelemy argued against stopping at the German-run hospital at Lambarene, Arnaud grew sicker and died, leaving a letter to his wife, Emily, back in Belgium. His body was thrown overboard in the Ogooué River. After reaching Port-Gentil, Defense mailed Arnaud's final letter.