Because he has difficulty obeying rules, midshipman Jack B. Austin is forced to repeat his final year at the United States Naval Academy in Annapolis and is assigned to oversee a shipment of new students. After weeks of intense drilling and instruction, Jack transforms his group of "plebes," which includes Russell H. Burns, an enlisted sailor, and the spoiled, wealthy Allen S. Williams, into presentable Navy men. However, while he is teaching his students the value of obedience and loyalty, Jack pursues Ruth Rogers, the daughter of his superior officer, and breaks curfew after a regimental hop to spend time with her. When Jack is caught sneaking to his dormitory by Clark Simpson, his friend and a rival for Ruth's affections, Clark reports him to Captain Rogers, who puts Jack on probation. Jack then learns from a disapproving Ruth that Russell had covered for him and was "put on report" as well. After lecturing Russell about protecting his career, Jack, whose proposal of marriage was turned down by Ruth, teams up with his students on a "sub chaser" boat race. Eager to win, Russell orders Allen, the helmsman, to change the boat's course and cut through a restricted seaplane landing area without consulting Jack. The boat crashes into a seaplane, and Russell, injured while trying to lessen the plane's impact, is rushed to surgery. Convinced that Russell's naval career will be over if he is held responsible, Jack accepts the blame for the accident and prepares to leave Annapolis. Before he goes, however, Russell regains consciousness and asks for him. While Ruth and her father listen, Russell admits that he changed the boat's course and tells Jack that all of the "plebes" respect and adore him. Impressed by Jack's confession that the "rules of the game are important," as well as his positive influence on his students, Rogers drops his investigation and allows Jack to graduate. Confident now that Jack has matured into a responsible Navy man, Ruth accepts his proposal.