Yves Montand and Charles Vanel play Mario and Jo, two schemers who attach themselves to one another only to discover that both are equally without prospects. After exhausting the commercial possibilities of the dusty border town they are otherwise unable to escape, they stumble across a dangerous but profitable opportunity: drive two trucks filled with unstable explosives through the mountains to a remote oil fire for a greedy American corporation. The experience not only tests their resolve as drivers, but as friends, and the two men soon find that their tenuous partnership may come at the expense of their very lives.
While there are many, many terrific scenes in the film, including the centerpiece explosion of a rock which has fallen into the path of the trucks, the most memorable comes after that, when Mario and Jo have more or less dissolved what was once a robust friendship. The two of them come across the site of an explosion that has ruptured a oil main, and a massive crater is quickly filling up with sticky, dark fluid. Jo reluctantly examines the situation, but Mario constructs a plan in order to successfully escape the pool of oil and put them back on track; unfortunately, his desperation – and frustration at the seeming uselessness of his onetime friend – overtakes his determination, and horrific tragedy strikes even as they seem to conquer this latest of natural obstacles.