Nick Carter, Master Detective
Nick Carter boards an airliner with John Keller, the inventor of a revolutionary new aircraft. The pilot makes an unscheduled landing so that his confederates can try to steal Keller's plans, but Carter holds them off, and stewardess Lou Farnsby manages to fly them to safety. Carter, posing as "Robert Chalmers", the new assistant to Hiram Streeter, the boss of the California factory, has Lou reassigned to the infirmary.
During his investigation, Carter receives the unwanted help of Bartholomew, who fancies himself an amateur sleuth.
A test flight of the new aircraft ends in disaster; the wings are ripped off during a high-speed dive, and the test pilot is killed. It is found that bolts attaching the wings were cut. Later, Carter finds Keller's body in a running car in a closed garage. Carter suspects Keller was strangled, and the scene staged to look like a suicide.
Finally, Carter notices that each time a part of the blueprints goes missing, a worker has a serious accident and has to be sent home. He surmises that sections of the plans have been photographed, and the film hidden under bandages. He goes to apprehend the plant's doctor, Frankton, but Frankton is forewarned. Unable to leave the factory in time, he has the unsuspecting Lou escort a "patient" home. When Carter arrives, Frankton tells him that Lou will be killed unless the doctor shows up at a prearranged rendezvous soon. Carter lets him leave, but secretly has the roof of his car painted with a white cross. This enables Carter to track Frankton in an airplane to a section of the Los Angeles docks. Frankton, his associates, the complete plans and Lou race to a waiting ship. Carter engages in a firefight with the crew using a Tommy gun borrowed from the police. He prevents their getaway, but he and his pilot are shot down. A harbor patrol gunboat arrives (at the instigation of Bartholomew), and the villains are forced to surrender.
murder