Two Royal Air Force officers, Flt Lt Hallett and F/O Neil Allison visit a British outpost in India.

Neil is the younger brother of Army Intelligence Officer Captain Jeffrey Allison who is away on an undercover mission in the unaligned and independent princely state of Lhanapur.

Upon the death of the elderly Maharajah of Lhanapur, Ramin Khan schemes to usurp the throne as a base for his revolt.

Disguised as an Indian holy man, Jeffrey gathers intelligence on Ramin Khan's insurgents whilst the British send a diplomatic mission to Lhanapur who are ambushed and killed.

Ramin Khan is delighted as he plans to ambush the British field force in a ravine near the caves of Kali.