Synopsis by Janiss Garza
Underwater photography was a novel technique in 1917 when this picture was made. It opens up in the early part of the 1800s, on an island in the West Indies. Marcel Lupin (Fred Radcliffe) has become marooned there because he loved money more than he loved his girl (Lillian Cook). Before committing suicide, he writes a note bequeathing his fortune to whoever finds it. A hundred years later, inventor John Fulton (Chester Barnett) is living in the same rooming house with a couple of sailors. One of the sailors is telling millionaire's daughter Dorothy Morgan (Barbara Tennant) the story of how he had found the treasure chest thirty years prior, but it fell into the sea when his boat overturned. Fulton overhears the conversation and suggests that his invention -- a periscope-like contraption that works underwater -- might help him. So they all head for Dorothy's father's yacht and search for the treasure. But there's a villain afoot who tries to foil their plans and keep the treasure for himself. Fulton manages to avoid a watery grave and, with the usual heroic turn, saves the day.