Blurb from the PDF:
The Ivory Trail is an adventure for the unofficial Hollow Earth Expedition plug-in Old West HEX. The adventure starts out as a Spaghetti Western but towards the climax the heroes will explore an ancient, Indiana-Jonesy underground complex with more cliff hanging than they may care for. The GM may even use the adventure as a starting point for an exploration of the Hollow Earth as the complex could extend deep into the Earth.
Blurb from the website:
Once upon a time in the Old West, three men robbed a bank and got away with a fortune. But the men started quarreling and finally the two underdogs shot their leader. They took the money and a pair of ivory-handled silver Colts. To avoid suspicion, the two men decides to hide the money and return to their jobs and families, waiting for the right time to fetch their reward. On their flight they stumbled over an ancient artificial cave complex. As the men explored the complex they decided that this would be an excellent place to hide their loot.