His reputation brought into disrepute by Captain Bagshaw, a competitor for the affections of Lady Jane Ponsonby, Bertram Oliphant "Bo" West decides to leave England and join the French Foreign Legion, followed by his faithful manservant Simpson. Originally mistaken for enemy combatants at Sidi Bel Abbès, the pair eventually enlist and are helped in surviving Legion life by Sergeant Nocker, although only after they discover that when he is "on patrol" he is actually enjoying himself at the local cafe with the female owner, Zig-Zig.
Meanwhile, Lady Jane, having learnt that Bo was really innocent, heads out to the Sahara to bring him back to England. Along the way she has several encounters with men who exploit the fact that she is naive and travelling alone. After several such run-ins, including with the Legion fort's Commandant Burger (who coincidentally had once been her fencing instructor, and joined the Legion in self-imposed shame after he had inadvertently cut her finger during a lesson), she meets Sheikh Abdul Abulbul and ends up becoming a part of his harem and planned 13th wife.
Nocker and Bo are kidnapped by Abulbul after being lured to the home of Corktip, a belly dancer at the Café ZigZig. Simpson follows them to the Oasis El Nooki but is also captured. After entering Abulbul's harem and discovering Lady Jane, Bo and Simpson give themselves up while Nocker escapes (or rather is allowed to by Abulbul) back to Sidi Bel Abbes to warn Commandant Burger of Abulbul's plans to attack Fort Soixante-Neuf (i.e. 69, the sexual position). However, during this time Zig-Zig has told the Commandant about Nocker's true destination when on patrol, and therefore upon his return his story is not believed. It is only when Nocker mentions Lady Jane that they realise he was telling the truth and the Commandant organises a force to reinforce the fort.
Along the way they discover Bo and Simpson staked to the ground at the now abandoned oasis. The relief column marches on towards the fort but heat, lack of water and a sand castle building competition gone wrong decimates the force to a handful. The remaining members reach the fort to find that they are too late; the attack has already occurred and the garrison wiped out.
After learning that Abulbul's celebration of the successful attack includes marrying Lady Jane, Bo, Burger, Nocker and Simpson rescue her from his tent, leaving Simpson behind dressed as a decoy. When Abulbul discovers the deception, he chases Simpson back to the fort where, through the imaginative use of a gramophone and a German marching song, gum arabic, coconuts, gunpowder and a cricket bat, the group holds off Abulbul's army until a relief force arrives. However, Commandant Burger ends up as the sole casualty among the protagonists.
Back in England the group reunites for a game of cricket, with Nocker having been promoted to Commandant and Lady Jane having conceived a son by the late Burger. Bo is batting, but when he hits the ball, it explodes. The bowler is then shown to be Abulbul having gained his revenge, to which Bo, with a broken bat and burnt clothes, good-naturedly responds "Not out!"
Phil Silvers as Sergeant Ernie Nocker
Jim Dale as Bertram Oliphant "Bo" West
Peter Butterworth as Simpson
Kenneth Williams as Commandant Maximilian Burger
Charles Hawtrey as Captain Le Pice
Joan Sims as Zig-Zig
Angela Douglas as Lady Jane Ponsonby
Bernard Bresslaw as Sheikh Abdul Abulbul
Anita Harris as Corktip
John Bluthal as Corporal Clotski
Peter Gilmore as Captain Bagshaw
William Mervyn as Sir Cyril Ponsonby
Julian Holloway as Ticket collector
David Glover as Hotel manager
Larry Taylor as Riff
William Hurndell as Riff
Julian Orchard as Doctor
Vincent Ball as Ship's officer
Peter Jesson as Lawrence (uncredited)
Gertan Klauber as Spiv (uncredited)
Michael Nightingale as Nightingale (uncredited)
Richard Montez as Riff (uncredited)
Frank Singuineau as Riff (uncredited)
Simon Cain as Riff (uncredited)
Harold Kasket as Hotel gentleman (uncredited)
Edmund Pegge as Bowler (uncredited)
Carol Sloane as Harem girl (uncredited)
Gina Gianelli as Harem girl (uncredited)
Dominique Don as Harem girl (uncredited)
Anne Scott as Harem girl (uncredited)
Patsy Snell as Harem girl (uncredited)
Zorenah Osborne as Harem girl (uncredited)
Margot Maxine as Harem girl (uncredited)
Sally Douglas as Harem girl (uncredited)
Angie Grant as Harem girl (uncredited)
Gina Warwick as Harem girl (uncredited)
Karen Young as Harem girl (uncredited)
Helga Jones as Harem girl (uncredited)
the 14th in the series of 31 Carry On films (1958–1992)
Like its predecessor Carry On Don't Lose Your Head, it does not have the words "Carry On" in its original title (though for screenings outside the United Kingdom it was known as Carry On In The Legion, and it is alternatively titled Carry On ... Follow That Camel).
It parodies the much-filmed 1924 book Beau Geste, by PC Wren, and other French Foreign Legion films.
Phil Silvers (in his only Carry On) is heavily featured in a Sergeant Bilko-esque role.