Beneath the forested flanks of an extinct volcano lies a cave with a mysterious secret. Kitum Cave on the slopes of Mt Elgon in Kenya is the only place on earth where elephants venture deep underground. They are forced to make the dangerous journey into the cave because of their craving for salt. Humans have been drawn to Kitum Cave for thousands of years, originally to harvest salt, but more recently to slaughter elephants, leading to local rangers Daniel and Mike being assigned to protect the survivors