Lure of the Islands (movie, 1942)

Tana, a voluptuous half-caste girl of the South Seas, falls in love with FBI agent Wally and wishes to marry him and leave the island. Wally, with his pal Jinx, is there to investigate rumored Japanese spy activity. He agrees to marry her if she will help him in his investigations. Through the discovery of a contraband radio set tuned to Japanese reception, Wally learns that the local Commandant is in league with the enemy and is planning an invasion of the island.