Set in the late 19th century at the height of the
British Empire, *Carry On Up the Khyber* unfolds in the turbulent, fictional Northwest Frontier province of Kalabar. The story centers on the illustrious Third Foot and Mouth regiment, affectionately known as the "Devils in Skirts," stationed at
the treacherous Khuff Kak Pass. Led by the unflappable Sir Sidney Ruff-Diamond, the regiment maintains a delicate peace with the fiercely proud local tribesmen, ruled by the charismatic yet scheming Khasi of Kalabar. The delicate geopolitical balance hinges on a bizarre cultural tradition: the tribesmen deeply respect the British solely because the regiment’s Highlanders wear traditional kilts without undergarments, a feat of stoicism the locals view as the ultimate display of martial bravery.Trouble brews when the Khasi, secretly plotting an uprising to drive the British out and reclaim the territory, discovers this scandalous secret. Motivated by a desire to humiliate the regiment and ignite a holy war, the Khasi orchestrates an elaborate campaign of espionage and seduction. Meanwhile, domestic tensions within the British residency threaten to derail the garrison from within. Sir Sidney’s sharp-tongued wife, Joan, engages in a bitter social war with the resident missionary's prudish wife, echoed by the chaotic romantic entanglements of the garrison's junior officers, who are easily distracted by the Khasi’s alluring female spies.The dramatic climax erupts during a high-stakes, formal dinner party hosted by Sir Sidney to appease the Khasi and maintain appearances. The Khasi executes his master plan by ordering his dancing girls to perform a synchronized routine designed to deliberately lift the Highlanders' kilts in front of the horrified, conservative British dignitaries. The resulting exposure shatters the illusion of British invincibility. With their secret revealed and their intimidation factor instantly dissolved, the rioting tribesmen attack the residency en masse.Chaos ensues as the regiment is forced into a frantic, slapstick defense of the fort using unorthodox weaponry and sheer chaotic panic. Despite the humiliation, Sir Sidney rallies his men, utilizing their remaining pride and sheer stubbornness to repel the onslaught until reinforcements arrive. The film concludes with the regiment successfully holding the pass against impossible odds, proving that military honor relies on far more than mere attire. Sir Sidney and his resilient troops manage to salvage their dignity, leaving the Khasi defeated and restoring a fragile, hilarious peace to the perilous mountain frontier.