Sir Sidney Ruff-Diamond arrives with his wife Joan in India in 1895 to take over as Governor of Kalabar. At a polo match, Randy Lal, the Khasi of Kalabar, intrigues Joan. Appearing outwardly civil to the British, Randy tells his daughter Jelhi that he would like nothing better than to kill them all and end British rule in India. While guarding the Khyber Pass, Private Jimmy Widdle of the Third Foot and Mouth Regiment stops Bunghit Din as he tries to cross the border. The locals fear the kilt-wearing regiment, calling its members the 'Devils in Skirts'. Bunghit tries to bargain his way through the border by offering some of his belongings. However, when he pulls out his scimitar, Widdle faints. Unable to resist, Bunghit lifts the kilt to see what is underneath. He takes the underwear and brings it to the Khasi.

Captain Keene reprimands Widdle for dereliction of duty. When he discovers that Widdle was not only wearing underwear, but also that a native has taken it, Keene immediately informs the Governor. Fearing that the revelation about Widdle's underwear could seriously undermine confidence in the British, the Governor and Keene go to see the Khasi. They find that the underwear has been mounted with other trophies and exhibited for everyone to see. Ruff-Diamond tries to convince the Khasi that this was an isolated incident and asks Keene to prove it by lifting his kilt. Unfortunately he declines as he is also wearing underwear.

Ruff-Diamond demands an immediate inspection for all his men. On the parade ground they all lift their kilts on command. Joan takes a photo proving that all the men do actually wear underpants beneath their kilts. Feeling disenchanted with her marriage, she goes to see the Khasi. She offers to trade the photo for sexual favours. Overhearing this, Princess Jelhi goes to see Keene and informs him that an insurrection will be inevitable if the tribesmen see the photo. She also tells him that her father has taken Joan over the border to Bunghit Din's stronghold in Jaksi to convince the tribe chiefs to revolt. Keene and Widdle go on a mission to retrieve the photo, with the missionary Brother Belcher acting as their guide. They disguise themselves as Burpas and gain access to the stronghold, where they are mistaken for the tribal chieftains. They are later captured when the real chiefs arrive.

Jelhi tells Joan that her father is planning to execute her with the captured officers. The two women spring the men from the jail and disguise them as dancing girls. They manage to escape from the stronghold with help from a fakir, but accidentally leave the incriminating photo behind. Arriving at the Khyber Pass, they find that an advance party of Burpas has killed all the British soldiers. With the Burpas in hot pursuit, they head back to the British residence.

They are soon surrounded, but the Governor insists that, being British, they behave as if nothing were happening. Dinner is served for the officers and guests. The Burpas attack with guns and cannons, but the British go ahead with the meal, seemingly oblivious to the explosions and gunfire. Brother Belcher becomes unsettled by their apparent indifference to the battle raging outside. When the perimeter of the British compound is breached, the men join the fight with the rest of the soldiers. When all seems lost, Ruff-Diamond has all the soldiers line up and pull up their kilts. The Burpas run away in horror. The Ruff-Diamonds and the British officers return to their meal, leaving the tidying up for tomorrow.