After preparing part of a southern California granite quarry for dynamiting the following morning, a work crew leaves the area. Eleven-year-old Bobby Ware and his pal, twelve-year-old Mickey Goodwin, then arrive on their bicycles to explore and play on the heavy equipment. Deciding to climb up to the top of a ridge, the boys hide their bicycles in brush to prevent theft and set off. Upon reaching the top, however, Bobby stumbles and when Mickey tries to catch him, both fall into a ravine, landing on a shallow shelf, halfway down the dangerous incline. When Bobby's father George returns home from work to his wife Janet and younger children Sammy and Janey, Janet tells him that Bobby is late in coming home, but George decides that Bobby may simply have been delayed by a flat tire on his bicycle. Meanwhile, Max Goodwin, Mickey's father, learns from his housekeeper, Sophie, that his son is late for dinner. Later, when Bobby has not returned, George phones Sophie for news of the boys and also checks with Bobby's homeroom teacher, who suggests that he contact the sheriff's station. Darkness has fallen and the boys, cold and scared, are still stuck on the ledge, hoping that people are looking for them. Bobby prays for protection throughout the night. After George unsuccessfully searches the neighborhood, he phones Max, who is dining at a restaurant with Alfred Gledhill and another business associate, and Max agrees to meet George at the sheriff's station. At George's request, Lt. Andy Flynn issues a bulletin to all patrol cars to be on the lookout for the boys and then arranges for a rescue squad, composed of professionals and volunteers, to be ready to begin a search at first light. George invites Max, who feels that he could have been a better, more accessible father to Mickey, to his house to wait for news. While they are there, a rock is thrown through a window. An attached note informs the fathers that if they want to see their boys again, they are to deliver ten thousand dollars in cash to a mailbox on an outlying road. Although George wants to inform the police about the kidnapping, both Janet and Max dissuade him and convince him to pay the ransom demand. At dawn, instead of joining Flynn's rescue crew to comb the nearby foothills, Max delivers the cash he has taken from his office safe to the drop point. George, meanwhile, decides to call off the search as the men and equipment might be needed for real emergencies, and locates Flynn close to the granite quarry. On the ledge, Bobby and Mickey hear an approaching helicopter, but it passes overhead and leaves without locating them. Although angered by the fathers' meddling, Flynn sets in motion a plan to trap the "kidnapper" when he appears to pick up the cash and also requests assistance from F.B.I. agent MacKay. Using stakeouts in unmarked vehicles, Flynn closes in on the kidnapper after he collects the cash and from his car's registration learns that he is Gledhill. Max then explains that Gledhill was with him when he learned that Mickey and Bobby were missing. The deputies pursue Gledhill in a high-speed car chase, which ends at a roadblock. Flynn and MacKay arrest Gledhill, who confesses to the extortion plot and then admits that he has no idea where the boys might be. Meanwhile, the blasting crew arrives at the quarry to begin the day's work. After Flynn reactivates the search party, he suddenly remembers that the blasting is about to begin and dispatches a squad car, which arrives just in time to prevent the explosions. The helicopter is in the air once more and the search crew is advancing through the area on foot when one of the men discovers the bicycles, which George identifies. As the helicopter approaches them again, the boys wave and this time are spotted by the crew. The ledge is impossible to reach on foot, so Flynn orders the helicopter to lower a harness and, in turn, both boys are lifted off the ledge into the helicopter. Bobby and Mickey are then reunited with their fathers.