Sir Sidney Ruff-Diamond (Sid James) is Queen Victoria's Governor in the Indian province of Kalabar near the Khyber Pass. The province is defended by the feared 3rd Foot and Mouth Regiment, who are said to not wear anything under their kilts. When a soldier, the inept Private Widdle (Charles Hawtrey) is found wearing underpants after an encounter with the warlord Bungdit Din (Bernard Bresslaw), chief of the warlike Burpa tribe, the Khasi of Kalabar (Kenneth Williams) plans to use this information to incite a rebellion in Kalabar. He aims to dispel the "tough" image of the Devils in Skirts by revealing that contrary to popular belief, they actually wear underpants underneath their kilts.