1914, East Africa. Gin-smelling Captain Charlie sails his steamboat to the Christian mission village of Reverend Samuel and his unmarried sister Rosa, who, amidst the wild African jungle, act as if they are still in good old England. But war is sweeping into Africa as well.

German soldiers storming into the mission burn down the village and hijack the inhabitants. The experience has badly affected the condition of the reverend, soon he dies, and Rose has to flee with Charlie. The prim missionary and the reckless captain, quarreling incessantly with each other, sail down the river on their way to dangerous and romantic adventures.