A group of young Girl Scouts who previously ran a charitable tea-house receive an unexpected invitation from a distant, unconventional relative to motor to California along the Lincoln Highway. The journey must be undertaken within a set budget, completed by a deadline, and carried out without accepting help from men, with the reward of a new runabout for each successful traveler. The narrative follows their planning and voyage, tracing road mishaps, mechanical and logistical problems, and shifting friendships, and emphasizes cooperation, practical resourcefulness, and the girls' growing independence as they meet challenges on the trip.