U.S. Secret Service agent Truxton Darnley attires himself as a sailor and boards a schooner owned by arms smuggler Gus Olsen, who is in the employ of German spy Von Linterman to smuggle arms to German raiders in the South Seas. Truxton learns Gus’s plan to blow up the National Munitions Plant in San Francisco, just before his identity is discovery and he is thrown overboard. Washed ashore on the island of Moana, Truxton meets native girl Lurline. Promising to return to her, Truxton boards a stea...