The guys are all taking it easy, one afternoon, in the McHale compound, when along comes Giuseppe Maggiore – McHale's Italian Cousin – On his bicycle. The guys all give Giuseppe a hearty welcome, and the ever-happy Giuseppe is glad to see the guys.
Soon, McHale hears the noise, and comes out of the tent, to see what's going on. McHale and Cousin Giuseppe are happy to see one another, and McHale asks Giuseppe what he's doing in Voltafiore. Giuseppe explains – In Italian, with McHale translating – That he's recently purchased a fishing boat, and has moved to the town of San Lucca, only about 10 miles away.
Later, in San Lucca, Binghamton and Carpenter exit from a meeting with General Grayson. Binghamton has come to report McHale and the 73 Crew with black marketeering, but Binghamton is only frustrated by The General's demand for proof.
As they make their way toward the jeep, Binghamton spots McHale coming down the street. He and Carpenter crouch behind the jeep, and watch, as McHale looks for the home of his Cousin Giuseppe. He soon finds it, and enters the building.
Carpenter wants to call the MPs, and have McHale arrested, right away, for being AWOL, but Binghamton holds off, his reasoning being that – If McHale were willing to risk being AWOL – What he's up to must be something really big, which may be the proof he needs for the black marketeering charge.
Meanwhile, McHale has made his way up to Cousin Giuseppe's apartment. After their greetings, Giuseppe leaves, with a large wine bottle, followed by his wife, daughter, and son.
When they step out of the apartment door, Binghamton and Carpenter – Thinking that Giuseppe is McHale – See Giuseppe kiss his family, and then head off down the street, with the big bottle. When they hear the daughter and son call Giuseppe 'Papa', they think that McHale is leading a double life, with a wife and family 'on the side'.
Again, Carpenter wants to arrest McHale right away, but Binghamton holds off. They could get him for having a 'black market family', but that would only be a paltry 10 years. Binghamton wants to wait, and nail McHale for "The big one". Desertion.
Later, in Voltafiore, McHale and Parker exit a small shop. McHale has purchased a birthday present for Giuseppe's son, Pietro, whose birthday is the following day. Parker expresses his concern that McHale will be sneaking away from the base again, but McHale is willing to take the chance, for he doesn't want to miss the Pietro's birthday.
Just then, Binghamton and Carpenter rush in. McHale tries to hide the present in the jeep, but Binghamton catches him. McHale protests, as Binghamton grabs the present, and begins to open it, thinking it might be some kind of illegal material, but he's somewhat surprised to see that it's a jack-in-the-box. Binghamton demands an explanation, and McHale is truthful, telling The Captain that the present is for his young Italian Cousin, up in the town of San Lucca. McHale asks for permission to make the trip for the party, but Binghamton flatly denies, and orders McHale out on a patrol mission to a place called Ramada Bay, to look for enemy submarine activity. McHale protests, knowing that Ramada Bay is quite shallow, and that no submarines could hide there, but has no choice but to give in, and follow The Captain's orders.
As McHale and Parker leave, Binghamton and Carpenter step away. Binghamton believes that McHale will ignore the orders, and make the trip to San Lucca, where Binghamton plans to nab him in the act of desertion.
Later, as the 73 makes it's way down the Italian coast, McHale orders Christy to make for San Lucca. Parker protests, for the course would be against Binghamton's orders, but McHale argues that Binghamton had ordered them to look for a submarine. So, their story will be that they spotted one, and followed it all the way to San Lucca. Once there, Parker and the crew will hide in a small inlet, while McHale attends the party.
Meanwhile, at Giuseppe's apartment, all the preparations have been made for Pietro's birthday party. Soon, McHale arrives, and is a bit worried, at first, when it seems that no one is home. Soon, Giuseppe's wife, Theresa, comes in. She explains that Giuseppe left, this morning, and hasn't returned. Then, when she spots an MP and a Policeman on their way to the apartment, she really begins to worry. McHale explains to Theresa that the MP is after him, for being AWOL. He asks that Theresa try to get rid of them, while he hides in the bedroom.
Theresa answers the door, and the MP asks to see Giuseppe, explaining that the Army suspects him of black market activity, and they want to ask him some questions. It seems that someone answering Giuseppe's description had been recently seen at the scene of a warehouse burglary, and the MP tells Theresa that – If Giuseppe is home – There is no way to connect him to it. Theresa explains that Giuseppe has just gone out to the back yard to chop some wood.
Overhearing all this, while Theresa stalls the officers, McHale quickly gets into some of Giuseppe's clothes, and makes his entrance, spouting off some angry Italian words. The policeman knows Giuseppe, and is a bit angry that the MP would accuse a good man of such behavior. The Policeman apologizes to Giuseppe, and he and the MP head for the door.
When the Policeman opens the door, Binghamton and General Grayson are outside. The MP snaps off a salute, as they enter, and Binghamton steps straight to McHale and Theresa, and introduces them as Mr. and Mrs. McHale. But McHale stays in character, and spouts off a few more sentences of Italian, and even shakes Binghamton's hand.
Binghamton doesn't buy the Italian act, but The General tells Binghamton that this man couldn't possibly be McHale, dressed as he is, and . adds that he probably doesn't even speak English. As McHale looks nervously at Theresa, she explains that her 'husband' and McHale are look-alike cousins. But Binghamton insists that 'Giuseppe' is McHale, and adds that – Not only is he secretly married to Theresa – He deserted his vessel, during a mission, and says that he can prove it, if they can take him back to Voltafiore.
The General reluctantly gives in, and agrees to take 'Giuseppe' back to the base, to try and get to the bottom of the situation, and firmly states that Binghamton had better be right. Binghamton returns that – When the 73 boat comes in, without McHale – They'll have all the proof they need.
Meanwhile, on the boat, Parker and the guys are beginning to worry, for McHale has been away for over 2 hours. Then, Willy comes up from below, with a report on a radio message from Voltafiore, from Fuji. Fuji reported that Binghamton and Grayson have taken Giuseppe in, and have him under arrest. Parker, now in command, decides that he and Gruber will go into San Lucca, find The Skipper, and figure out their next move.
Meanwhile, the real Giuseppe has returned to his home, and, when Parker and the Gruber get there, they think he's McHale. Relieved, Parker is about to leave, but Theresa explains that McHale switched places with Giuseppe in an effort to protect Giuseppe, and that it was McHale who had been arrested.
Gruber quickly figures out that – If they return to base without their Skipper – McHale could be nailed for desertion, and he quickly comes up with the idea of having Giuseppe pose as McHale, long enough to get the Skipper out of trouble. Parker agrees with the idea, and, after Theresa explains to her husband, Giuseppe very much likes the idea.
But… There's one major problem. Giuseppe doesn't speak English. So, Gruber quickly decides that they simply teach Giuseppe a few English phrases that McHale would normally use, and they should be able to squeak by. The first lesson takes place immediately, and, after they get around a few minor accent adjustments, Giuseppe does very well.
Later, as the 73 nears Voltafiore, Parker runs Giuseppe through some of the English phrases they've taught him, while, at the dock, Binghamton, Grayson, McHale, and Theresa await their arrival. When The Captain and The General go to the dock, Theresa quietly explains to McHale that Gruber has come up with a plan – An idea that makes McHale a bit nervous.
When the 73 pulls in, Parker steps down, and reports that they had not sighted any submarine activity, on their mission. Binghamton then demands that they produce McHale, and Giuseppe makes his entrance.
Binghamton is very surprised, as well as disappointed, and Grayson has all the proof he needs. Then, after some of the guys compliment The Skipper on a job well done, Parker secretly signals Giuseppe, and he lets loose one of the English phrases he's recently learned.
"KNOCK IT OFF, YOU GUYS!" Giuseppe shouts, with just a hint of an Italian accent, but sounding very much like McHale.
"Commander…" begins Grayson, as he gives Binghamton a hard look. "Captain Binghamton and I would both like to apologize to you, and to your Cousin."
"HOW DID YOU GOOF BALLS EVER GET IN THE NAVY?!" Shouts Giuseppe.
"This man is a General!" says Binghamton, angrily. "You can't talk to him like that!"
"SHAPE UP, OR SHIP OUT!!" returns Giuseppe, as McHale cringes.
As Parker tries to stammer out an explanation, McHale rushes up onto the boat, to give his Cousin a big welcome-home hug. Binghamton threatens to throw McHale into the brig, for insubordination, but Grayson tells him he'll do nothing of the kind, for they must keep everyone happy, to keep Giuseppe from suing them for false arrest.
Then, Giuseppe's children – Angelina and Pietro – Rush up onto the dock. But McHale rushes over, and tells them, in Italian, to say bye-bye to 'Cousin McHale'. Grayson and Binghamton then step over, and The General orders The Captain to apologize to 'Giuseppe', which he reluctantly does. After Grayson then tells Binghamton that he'd like to see him in the office for a nice, long talk, he turns toward the boat.
"So long, McHale!" says The General, with a wave.
"KNOCK IT OFF, YOU GUYS!" returns Giuseppe, with a wave.
Just then, a report comes over the radio, on the sighting of a German submarine, nearby. Giuseppe is, of course confused, and McHale panics. He tries to board the boat, but Binghamton stops him, and Grayson orders them to get underway. McHale shouts to Giuseppe, in Italian, explaining that he must go with the boat, and Parker hustles Giuseppe toward the helm.
"KNOCK IT OFF, YOU GUYS!" shouts Giuseppe, with a smile, as Parker gets the 73 cranked up, then he adds: "HOW DID YOU GOOF BALLS EVER GET IN THE NAVY?!"
'Giuseppe' and Theresa wave bye-bye to 'Cugino McHale', as the 73 backs away from the dock, and Grayson and Binghamton look at one another, questioningly.
Later, in the wine cellar, McHale is a bit worried, that Parker and The Crew are way overdue, and he and Fuji pace back and forth. But, soon, Giuseppe and the guys come home, much to McHale's relief. Parker then explains that they'd chased the Kraut sub into a narrow channel, with Giuseppe's knowledge of the local waters helping them through. Parker goes on to say, however, that they'd missed the sub, which makes McHale pretty angry.
"WHY YOU EIGHT-BALLS!!" shouts McHale. "YOU GOT ME ALL WORKED UP…"
But Cousin Giuseppe cuts him off with:
"KNOCK IT OFF, McHALE!!"
After Parker and the guys get a laugh, McHale salutes his Cousin, with a smile.
"Aye-aye, sir!" he says, then: "That's my Cugino!"