Set in the jungle of the Congo Free State in 1887–88, the story begins after explorer Henry Morton Stanley, has gone to relieve Emin Pasha, governor of Equatoria, from a siege by Mahdist forces. He leaves behind him a 'rear column' with supplies at the Yambuya camp on the Aruwimi River and instructs them to wait until the Arab slave trader, Tippu Tib, has brought 600 more porters before following on to Equatoria. The play follows the story of the men left waiting in the camp. The officers depicted in the play are based on historical figures.