The story:

The disgraced Buba of Llongo tells two of his fellow inmates about a priceless treasure beyond anybody's expectations hidden deep inside the Phantom's Skull Cave in the Deep Woods.

When another inmate arranges an escape with the help of a rich backer, the now well-funded and well-resourced group prepares for an all-out assault on the Phantom's inner sanctum employing deception, posion gas and a small army...