A raft carrying a little girl and a dead woman drifts in from a shipwreck to Devil's Island. There, a band of thieves and smugglers name the girl Rose Marie, though she grows up as "nobody's girl." Living in a cave, she learns to read through the kindness of Jason, who is soon killed by the cruel leader, Red Gull. In Red Gull's power, and urged on by Jason's jealous wife, Rose Marie makes her escape in a rowboat, where she is spotted by an aviator flying above the sea. He rescues her, taking her to be cared for at his home where she is well treated. When newspapers report a mysterious shipwreck on Devil's Island, Rose Marie reveals the way in which Red Gull lured ships to their doom there. She guides the authorities to the island, where, after a fierce battle, the thieves are wiped out. Eventually the aviator falls in love with Rose Marie, and "nobody's girl" is somebody's sweetheart at last.