Secret Service of the Air

In this thriller, a Secret Service agent discovers a smuggling operation bringing illegal aliens from Mexico by small plane. After his murder, the operation is shut down, but the agent's death sparks a new investigation. An ex-Navy flyer, now flying the Pacific Clipper route, is recruited by the Service to track down the smugglers. He goes undercover in prison to gather intel from an ex-smuggler and eventually infiltrates the ring to capture the mastermind and bring them to justice.