McHale, the 73 Crew, Captain Binghamton, and Lieutenant Carpenter have all been transferred to a base in the little coastal town of Voltafiore, Italy, and soon find themselves dealing with the town's crooked, money-hungry Mayor.
While in search of a hot shower, McHale, Parker, Gruber, and Tinker are trapped by a German patrol, behind enemy lines, and must masquerade as an Italian family, in order to save themselves, as well as The Captain and Lieutenant Carpenter.
Binghamton angers the local Italians, after forbidding their fraternization with Naval personnel, but must quickly make amends with them, in order to please a certain VIP, due soon, for a visit. So, he reluctantly allows McHale and the townsfolk to throw a big wedding bash for a young Italian woman, and her fiancée - A soldier in the Italian Army.
Gruber and the guys find that there is money to be made, in the lucrative German war souvenir market, and, after they, McHale, and Colonel Harrigan are all captured by a German patrol, during a souvenir-hunting trip to an off-limits town, Parker and Fuji collaborate on a clever plan to rescue their comrades.
After Binghamton throws Parker into the brig, under several unfair charges, McHale and Mayor Lugatto must cooperate in a plan to turn the glory-hungry Binghamton into 'The Great Liberator', as part of a plan to get the Ensign out of the slammer.
After both Binghamton and Harrigan catch McHale and the guys having some unauthorized R&R in the home of an Italian Contessa, they have no choice but to go along with the plan of having Parker pose as the Contessa, in order to try to fool General Bronson, and keep everyone out of trouble.
After General Bronson cracks down on wartime profiteering, Mayor Lugatto tricks McHale into going into the fishing business with him, a situation which, quite unintentionally, works out for the good for McHale and the crew, but very much not-so-good for Binghamton and Lugatto.
Fed up with their less-than-pleasant accommodations, McHale and the guys move to an abandoned wine cellar, and furnish it with some luxurious furniture, found during a mission. But, after first Binghamton, then Harrigan impound their furnishings for their own use, McHale and the guys must come up with a scheme to get it back, and keep it.
Binghamton is determined to get hold of a stash of stolen rare wine, for a gift to the General; Mayor Lugatto wants the wine for it's cash value; And McHale and the Crew just want to see that it's returned to it's rightful owners, and to get back at the Germans who stole it, in the first place.
Mayor Lugatto wants the town's opera house back in business, and McHale wants his Crew out of jail. So, they cooperate in a plan to accomplish both, by having Binghamton sing the lead in the opera company's season-opener, despite The Captain's painfully obvious lack of talent.
Binghamton throws Mayor Lugatto into jail, pending impeachment proceedings for running a racket, in the form of a 'Good Luck Fountain', in the town square. So, to get The Captain to let The Mayor out of jail, and reopen the fountain, McHale and the guys must come up with a plan to convince Binghamton that 'The curse of Voltafiore' has befallen him.
After Colonel Harrigan cons Binghamton into moving the 73 Crew into town, so that he can take over McHale's beach, McHale and Binghamton carry out similar, but conflicting plans to get back at the Colonel.
Binghamton has the evidence he needs to court martial McHale and the 73 Crew, and has summoned the Judge Advocate General, to present it. McHale and the Crew must then execute a very complicated plan to get Binghamton to reveal the whereabouts of the evidence, so that they can get rid of it, before the JAG arrives.
After McHale defies Binghamton's orders, and travels to a nearby town, to attend his little cousin's birthday party, Binghamton tries to nail him on a desertion charge. But McHale manages to stay out of trouble, when he and his look-alike Italian Cousin, Giuseppe, assume each other's identities long enough to fool Binghamton and General Grayson.
Parker tries, unsuccessfully, to set 3 young Italian thieves on the straight and narrow, with some good old-fashioned Boy Scout training. But, after McHale and the Crew are arrested and jailed for the gang's crimes, the boys set out to help their Scoutmaster and his Crew, and wind up nailing Binghamton, in the bargain.
Gruber and the guys find a way to both make and deliver their homemade liquor when they build a mobile distillery in an old fire engine. But their scheme goes sour, when Binghamton confiscates the old engine for the new Voltafiore Volunteer Fire Department, formed as a part of his new civic improvement program.
Parker takes it on the lam, after an accident with a machine gun has him thinking that he's killed The Captain. After the furious Binghamton orders an all-out search for Parker, and offers a sizeable reward for his capture, McHale and The Boys must first find him, then cook up a complicated plan, to get him out of trouble.
After Binghamton arrests an AWOL WAC Corporal and jails her on suspicion of espionage, Parker must play the part of a WAC MP, as part of McHale's plan to free her, and reunite her with her boyfriend, before her unit ships out to North Africa.
Binghamton devises a scheme to make McHale and the 73 Crew look bad in the eyes of a visiting Congresswoman. But, after McHale and the guys scheme their way out of the jam, Binghamton must then cooperate with them, in order to get himself out of a tough situation with the Congresswoman, and get back at Harrigan, at the same time.
When Binghamton loses $1000 of Navy money to an Italian con man, for the construction of a new golf course, he enlists the aid of McHale and the 73 Crew in not only getting the money back, but making a fool out of Colonel Harrigan, as well.
After learning that German spies are operating in the area, Binghamton arrests McHale and Parker for espionage, thinking that they are working with a mischievous monkey, who has stolen an important document.
A regulation-quoting lady Ensign tries to help McHale and the Crew make some much-needed money, by providing the participants for a beauty contest, and winds up helping them bag a German submarine, in the bargain.
Thinking that McHale has been shipped out, and fed up with the power-drunk Parker, Gruber, Virgil, Tinker, Christy, and Willy, all put in for transfers. But, when they find out that McHale's absence is only temporary, Parker and the Crew must come up with a plan to get The Captain to tear up the transfer papers.
In the midst of the town's 500th anniversary celebration, Binghamton tries to arrange to have a visiting Psychiatrist declare the 73 Crew unfit for duty, forcing the newly-crowned 'King Of The Festival' to come up with a plan to keep his Crew together, and turn the tables on The Captain.
During an attempt to impress a famous War Correspondent, Binghamton is taken prisoner by a German patrol, who have disguised themselves as American Sailors. After Parker is also captured, McHale and the guys come to the rescue, and wind up having their picture on the cover of a popular magazine.
McHale and the Crew have a jeep that needs an engine; A local race driver has an engine that needs a car; The Army wants to get hold of one of the Germans' new staff cars - And all 3 are accomplished during the town's annual Grand Prix auto race.
Concerned about Parker's unusual behavior, McHale and the guys investigate his situation, and are a bit shocked, when they find that he's involved with a cute young thing named Angelina, who happens to be in a family way.
A trigger-happy Italian Count challenges Parker to a duel, and, while McHale and the guys try to help him out of the situation, Binghamton tries to use it as a way to get rid of both Parker and McHale.
A big-shot Washington Political Boss - With a reputation for turning war heroes into politicians - Is about to pay a visit, and Binghamton must quickly change from a 'desk jockey', into a fearless, battle-hardened Commander in order to try to become the Boss's next project, after the war.