In a remote area of the Mojave Desert, mining engineer Joseph Duncan and his lover, Geraldine Carson, lay a false trail to convince searchers that Gerry's husband, millionaire Donald Whitley Carson III, wandered off into the desert after his car broke down. Upon their return to the dude ranch at which they are staying, Gerry and Duncan tell the staff that Donald, drunk and impatient with the slowness of their trek on horseback, left and took the car. Unknown to Sheriff Vincent and others who begin to search for Donald, while Donald, Gerry and Duncan were riding through a distant canyon to investigate Duncan's manganese claim, Donald fell off his horse and broke his ankle. Leaving him a blanket and a small amount of food and water, Gerry and Duncan claimed to be going for help, but instead decided to leave Donald to die and lead searchers in the opposite direction. Gerry soon returns to the Carsons' Los Angeles mansion to alert Donald's lawyer, Dave Emory, that Donald has disappeared. At first Dave is not concerned, as the tempermental, alcoholic Donald has gone missing before. Eventually, however, when the trackers can find no further trace of Donald after following the false trail, it becomes obvious that Donald is truly lost. Meanwhile, in the canyon, Donald has deduced that Duncan and Gerry have betrayed him, and despite their belief that the spoiled millionaire would simply give up and shoot himself, he resolves to return to civilization to obtain revenge. After painfully setting his broken ankle with a makeshift splint, Donald manufactures a rope with pieces of the blanket and begins the difficult process of lowering himself to the canyon floor. Pain and exhaustion threaten to overwhelm him, and he panics when some of the precious water in his canteen spills out, but nonetheless perseveres. Back at the guest ranch, Dave has arrived with Gerry and Duncan to continue the search, and Duncan reassures Gerry that once it rains and wipes out any tracks they left in the canyon, they will be completely safe. The lovers decide not to see each other until it rains, to avoid suspicion, and return to Los Angeles after Dave leaves on business. After a week goes by, Donald finally reaches the bottom of the canyon, and just as he wonders if he will die from thirst, he finds some barrel cactus and uses his knife to dig out the moist tissue inside. Donald then spots an abandoned mine shaft and uses one of the timbers to make a crutch, but his triumph turns to despair when a coyote steals a rabbit he has shot. Uncertain that he will live to have his vengeance, Donald sits at the canyon bottom, and as he muses on the cycle of the seasons, he realizes that there must be water beneath the canyon floor. After digging a waterhole, Donald uses his last bullet to kill a small deer, then dries the meat in the sun. While Donald is congratulating himself on his resourcefulness, it finally begins to rain, and in Los Angeles, Duncan and Gerry are thrilled that their plan seems to have succeeded. With a supply of meat and water, Donald begins to hobble through the desert and periodically lights fires to attract attention. He is thrilled to see an airplane overhead one day, but when the plane circles the canyon, he realizes that it must be Duncan checking to see if he has died. The pilot is indeed Duncan, who reports to Gerry that Donald's blanket is gone and a waterhole has appeared in the canyon bottom. Fearing that Duncan saw his signal fire, Donald moves as fast as he can, although he knows that Duncan can find him. The next day, Duncan and Gerry drive out to the desert to kill Donald, and while Gerry watches with binoculars from the car, Duncan stalks Donald. Just as Duncan is about to shoot Donald, however, the relieved millionaire is picked up by prospector Sam Elby, who was driving his ancient jalopy from town to his desert home. When Duncan returns to his car, he discovers that Gerry had tried to leave him behind but drove the car into a rock and broke the crankshaft. Duncan angrily sets off to walk to town, with Gerry following and pleading for him to wait. While Donald eats and rests in Elby's shack, Elby questions him about his plans. Donald realizes that his experiences have changed him, and that his wealth is no longer the most important thing in his life, nor does he hunger for revenge any longer. Meanwhile, Duncan leaves Gerry behind and reaches the shack. Realizing that he can salvage the situation, Duncan knocks Elby unconscious when he goes outside to fetch water, then enters the shack and engages in a fierce fistfight with Donald. During the struggle, the stove is knocked over and starts a fire, and Donald is able to knock Duncan out before collapsing himself. Elby revives and drags Donald to safety just before the roof caves in and kills Duncan. In the morning, Elby and Donald are driving to town when they find Gerry staggering along the road, and Donald tells her that she can either come with them or wait for the sheriff to pick her up.