Do or Die
This 18-part serial, starring Eddie Polo, was released on May 30, 1921. Some scenes were filmed on California's Santa Catalina Island, although many of the scenes were said to be filmed in Cuba.
An American family lives in Cuba and owns a special ring that contains a map to buried pirate treasure. A guy named Satan is the bad guy. (What else could he be with a name like that?) Satan tries repeatedly to gain possession of the ring.
A member of the family from the United States goes to Cuba to help combat Satan. He finds it's not as easy as it sounds because it takes 18 hellish episodes to defeat the forces of evil, but Eddie Polo saves the day and the map. (I just love the image on this poster.)