In order to claim a region of African land for England, ambitious inventor Samuel Fergusson (Cedric Hardwicke) creates a large balloon with an elaborate space for passengers. Among those joining Fergusson on his extended expedition are his dutiful assistant, Jacques (Fabian), as well as beautiful teacher Susan Gale (Barbara Eden) and hapless reporter Donald O'Shay (Red Buttons). Along the way, the group encounters a shifty slave trader (Peter Lorre) and various other eccentric characters.