When Chip announces Tramp is the father of six puppies, Steve is concerned because he has never explained the cycle of life to his son. But before long a confused Chip thinks that his teacher is going to marry his father.
The good neighbour policy gets a real workout when the boys, and later Bub, tangle individually with members of the new family across the street. Steve lectures them but on his way to work as he's backing out the driveway, he is delayed by a fender-denting idiot who turns out to be none other than Mr. Kaylor - the neighbor across the street.
Mike has found a girl at college, Mary Beth. But when he brings her home to meet the family, she makes a beeline straight for Steve, who is trapped into tutoring her in trigonometry. This gives Mike a few jealous moments until all is resolved.
When a boiling pot explodes Tramp's barking wakes the family saving them.
An old high school sweetheart calls for Steve while he is out. Feeling nostalgic, Steve tries to locate her in town, but never seems to be able to catch up with her as he reminisces about their past relationship. As he arrives home the door bell rings and he gets a disappointment then a surprise.
Bub and Mike are at odds with each other because both are trying to get into different, exclusive clubs. Bub is to be installed as the D'Artagnon of the East Door, while Mike is subjected to his initiation which involves pretend fishing in front of the local drug-store.
Mike wants to go skiing on the weekend with his friends but must also keep up his Spanish studies. So he adopts the learn while you sleep method via use of a pre-programmed record player. Steve's room has just been painted so he decides to sleep in Mike's bed. Mysteriously, he wakes up speaking Spanish, and the next night Bub does the same. Before long they are both uttering phrases they couldn't possibly know.
Robbie is heading for an ‘F' in world literature until the teacher assigns a beautiful blonde newcomer as his study partner. He is attracted to her right away but soon discovers that her looks don't even compensate for her loss of mind.
A composition titled ‘What My Mother Means to Me' has Chip baffled. After interviewing other mothers in the neighborhood, he makes a courageous effort to improvise by writing about his own Grandfather, whom he feels is the most maternal person he knows.
Steve and Bub are both called out of town and Mike urges them to leave him in charge, only to find the role of mother hen harder than it looks. His worth is really put to the test when he learns that Robbie and Hank have been taken to hospital after an accident at school.
Bub decides to go to night school when he finds that his grandsons keep asking endless questions that he simply cannot answer. He meets a fellow student and passes himself off as a former show business producer, while she makes out she's a high society dame, when in fact she's really a maid.
Robbie's band rehearsals upsets the household. Mike's fraternity is looking for a band and Robbie tries to get the job.
When Robbie and his friend Hank decide they want to join a club at school, Robbie insists he does not want to join Mike's old club. When he gets an offer to join the Chieftains, the one school Club his brother never belonged to, he jumps at the chance.
Chip feels ignored by his family and decides to do them all a favour by running away from home. His solution is to strike away for far-east India very early the next morning. He takes fright while downtown and secretly returns home and hides in the attic, forgetting the farewell note he's pinned to Tramp's collar.
Steve takes a week's vacation from the family where he soon finds that he can fall in love with someone as easily as fall out of love with them. Sure that an older couple he's met are trying to play matchmaker, Fran is unsociable towards Steve at first until he points out that he only came along on the trip to appease his fellow campers.
Two dates, confused phone calls and name mix-ups create a tangled evening for brothers Mike and Robbie, when each get's the other's date. Mike gets a shock when he picks up a fourteen year old, while Robbie nearly croaks at the sight of his 'older woman'.
Attractive Pamela MacLish whom Steve took to Chip's grade school dance a year ago, is still trying to melt his bachelor heart. She arrives at the house on the pre-text of soliciting Bub's help to join an Irish Society called the 'Daughters of the Emerald Isle'. Soon Bub thinks that Pamela is after him.
Four beautiful airline stewardesses move into the vacant house next door and Mike and Robbie immediately are attracted to the glamorous career women. Meanwhile Steve is at the drawing board trying to meet a work deadline that requires his total concentration.
Bub reads an article in a magazine which is directed at bored homemakers and he begins to think that he fits the description. Steve warns him that he should control his Irish temper as it could lead to the demise of his position should he find one.
Steve is going to Chicago on business and he's promised to take Chip with him. A change of plans sees Steve boarding a military plane bound for Paris. Chip takes action when he finds out that he can't go on a trip to Paris with his father, by sneaking onto the plane. He gets lost in the city and is befriended by a little girl named Marie.
Bub fires Robbie's show business ambitions when he tells him to make the most of an opportunity when Robbie's 9th grade physics class is the subject of an educational film. He is excited when he and a fellow student are told they will be part of a close-up scene.
Chip tries to snow his teachers so he can win an art contest and almost succeeds with some help from Bub, who actually painted the artwork. Chip's teacher offers his painting to the Principal to show the school board. When Chip learns of this development, he plots with Sudsy to steal it back.
The Douglas family goes to the train station to meet Steve but when they prepare to leave, they can't find Tramp anywhere. Tramp has wandered into the cabin of a famous actress named Marissa Montaigne who takes a liking to him.
Robbie finds out that he won't be able to play in the big game unless he passes a math exam. Steve assures him that if he fails he will not be playing against his team's arch rival. When Chip comes down with the measles, it dampens Robbie's attempt to play even more than before.
Chip's schoolmates want to help him celebrate his tenth birthday with a party but he doesn't want to share the occasion with certain young ladies. However, Steve falls foul of the German measles and when Bub speaks to Sudsy's mother about it, suddenly the gossip mongers decide that they will not send their children to the house for fear of catching the disease.
Steve's friend asks him to come up with a solution when she thinks her daughter is dating an older man. Steve is shocked when he sees that the initials of the fraternity pin the man gave her identifies his oldest son Mike. However it is really Robbie who took the use of Mike's pin to fix his button-less shirt.
Chip puts his father into the uncomfortable position of defending the importance of his profession. Chip is unenlightened by the tour of the Air Force base until a full-scale emergency arises and Steve is asked to help a desperate pilot down from the air.
When Steve and an old boyhood pal discuss the time they ran away to another town, Mike and Robbie, who are continually in need of cash, decide that during school vacation they will go North to the next big town and try and get jobs.
At the suggestion of his best pal Hank, Robbie plans to earn some extra pocket-money by caddying at the local Golfing Tournament. He's assigned to the most temperemental golfer on the course. At the 18th hole Robbie accidentally kick's the ball out of the rough, immediately disqualifying his golfer from the competition.
Steve's wish for a calm life sends him on a chaotic journey into a parallel universe when on a typically rambunctious morning, the Douglas household noise is ruining Steve's day off from work. So he gets in his car to get away from it all, wishing that he'd had girls instead of boys.
Robbie's only real competition for winning a school scholarship in a model airplane contest is a young boy named Roly Bates, a studious lad who has his heart set on first prize as its his only chance to get a college education.
Mike has problems with his girlfriend's father when Mike tries to see another girl.
On his first day in High School, Robbie has some memorable highlights -- such as being assigned a locker with Chug Williams, the school's star senior athlete. When it is evident that Chug is using Robbie, Mike tries to warn him that he has become the victim of a dangerous case of hero-worship.
Steve pushes Chip to go on a week-long vacation with a boy he really doesn't like. The boy is very shy and timid, and when Chip calls him a chicken-clunk, he cops an unexpected black eye for his trouble. Meanwhile Bub tries his hand at painting.
Mike faces disciplinary action at the hands of the Board of Regents and the Dean of the College for a wayward fraternity prank in which several of the students have created a foot-print mould which bears a remarkable resemblance to the hippopotamus.
Two of Bub's cronies who are visiting for their usual game of pinochle, accidentally get an earful of the family's woes. Their mysterious interjection to try and solve the problems, leaves Steve and the boys quite baffled.