In Timbuktu, experienced guide Joe January (John Wayne) reluctantly joins a Saharan treasure hunting expedition led by Paul Bonnard (Rossano Brazzi), a man obsessed with confirming his dead father's claim to have found a lost city. Dita (Sophia Loren), a woman of dubious reputation, becomes infatuated with Paul and his willingness to overlook her past. She invites herself along, despite Joe's protests. During the tough dry ordeal, Joe and Dita become attracted to each other, raising tensions.