The story:
An explorer called Wells is struck down with jungle fever but saved by the Bandar and brought to the Deep Woods, where he witnesses the annual ritual of the Phantom honouring his ancestors by drinking out of a giant diamond cup that once belonged to Alexander the Great.

Back in the Explorer's Club in Bengali, Wells relays his story and is goaded into a hefty bet by the unscrupulous Lorgen, who sends his sidekick Trigger as a guide with Wells to re-enter the Deep Woods and verify the claim... and to steal the cup.