Outlaw Johnny Finger, better known as The Rumpo Kid (Sid James), rides into the frontier town of Stodge City, and immediately guns down three complete strangers, orders alcohol at the saloon—horrifying Judge Burke (Kenneth Williams), the teetotal Mayor of Stodge City—and kills the town's sheriff, Albert Earp (Jon Pertwee). Rumpo then takes over the saloon, courting its former owner, the sharp-shooting Belle (Joan Sims), and turns the town into a base for thieves and cattle-rustlers.
In Washington DC, English "sanitation engineer first class" Marshal P. Knutt (Jim Dale) arrives in America in the hope of revolutionising the American sewerage system. He accidentally walks into the office of the Commissioner, thinking it to be the Public Works Department, and is mistaken for a US Peace Marshal, and is promptly sent out to Stodge City.
The Rumpo Kid hears of the new Marshal, and tries all he can to kill the Marshal without being caught, including sending out a pack of Indians, led by their Chief Big Heap (Charles Hawtrey) and hanging the Marshal after framing him for cattle rustling. Knutt is saved by the prowess of Annie Oakley (Angela Douglas), who has arrived in Stodge to avenge Earp's death and has taken a liking to Knutt.
Eventually, Knutt runs Rumpo out of town, but once Rumpo discovers that Knutt really is a sanitary engineer and not the Peace Marshal he once thought, he swears revenge, returning to Stodge City for a showdown at high noon. Knutt conceals himself from Rumpo's gang in drainage tunnels beneath the main street, emerging momentarily from manholes to pick them off one by one. He does not capture Rumpo, who escapes town with the aid of Belle.
Sid James as Johnny Finger/The Rumpo Kid
Kenneth Williams as Judge Burke
Jim Dale as Marshal P. Knutt
Charles Hawtrey as Big Heap
Joan Sims as Belle Armitage
Peter Butterworth as Doc
Bernard Bresslaw as Little Heap
Angela Douglas as Annie Oakley
Jon Pertwee as Sheriff Albert Earp
Percy Herbert as Charlie
Sydney Bromley as Sam Houston
Edina Ronay as Delores
Lionel Murton as Clerk
Peter Gilmore as Curly
Davy Kaye as Josh
Alan Gifford as Commissioner
Brian Rawlinson as Stagecoach guard
Michael Nightingale as Bank manager
Simon Cain as Short
Sally Douglas as Kitikata
Cal McCord as Mex
Garry Colleano as Slim
Arthur Lovegrove as Old cowhand
Margaret Nolan as Miss Jones
Tom Clegg as Blacksmith
Larry Cross as Perkins
Brian Coburn as Trapper
Ballet Montparnasse as Dancing girls
Hal Galili as Cowhand (uncredited)
Norman Stanley as Drunk (uncredited)
Carmen Dene as Mexican girl (uncredited)
Andrea Allan as Minnie (uncredited)
Vicki Smith as Polly (uncredited)
Audrey Wilson as Jane (uncredited)
Donna White as Jenny (uncredited)
Lisa Thomas as Sally (uncredited)
Gloria Best as Bridget (uncredited)
George Mossman as Stagecoach driver (uncredited)
Richard O'Brien as Rider (uncredited)
Eric Rogers as Pianist (uncredited)
the eleventh in the series of 31 Carry On films (1958–1992).
It was the first film to feature series regulars Peter Butterworth and Bernard Bresslaw