The Pearlhunter (sic) and his mother live on the Wabash River in a houseboat. He does not know his name. His father deserted his family when he was a child, and the mother desires to keep it a secret. They go to a cabin on shore. Later, while gathering herbs in the woods he comes upon a young girl. She drops her wild roses and disappears. That evening a stranger enters the young man's house and orders him to leave: The mother recognizes him as the man who lied about her to her husband. The Pearlhunter throws him out. A tiny red mask dropped by the man shows that he is the bandit who has been terrorizing the vicinity. The Pearlhunter discovers a "Blue Moon" pearl. He hurries home to tell his mother the great news, which means health for her and wealth for him, and finds her dead.
He goes to the "wild rose's" home and tells her the story. Then going to the cabin he finds the "red-mask villain" and follows him to where he has hidden the "blue moon." The sheriff, "who is with him, fires but the bandit escapes In the darkness. They follow him to the home of "Wild Rose," and prevent him from abducting the girl. He Is shot by the sheriff and confesses the truth about the pearl hunter's mother. All ends happily.
- “Newest Reviews and Comments.” Moving Picture World, 1 Jan. 1921.
Some scenes were shot at the newly created Bird Refuge in Santa Barbara but filming locations also included The Upper Wabash and Flatwoods of Indiana according to the Moving Picture World.
- “New Types and Locations All Combine to Popularize American’s ‘Blue Moon.’” Moving Picture World, 8 Jan. 1921.
Sidney A. Baldridge was given full charge of the settings. David Anderson, author of the novel the movie was based on, was in charge of the titling.- Moving Picture World, 23 Oct. 1920
Daniel Whitcomb created the continuity script and Sid Algier was the assistant director.