The characters are smugglers, taking things from Havana, Cuba, to Key West, Florida. They're part of a big, creepy organization with a lot of secrets.
On this particular trip, the characters take a typical load of barrels but also a mysterious box they have been told not to open. They will soon discover the box contains a magical statuette. If it reaches the United States, it will be used in a ritual that will raise Cthulhu from the Sunken City of R'lyeh...
This scenario is distributed as a ZIP archive containing five PDF files - a 10-page scenario, and four 1-page pre-generated characters.