Aeronautical Engineer Steve Douglas and his youngest son Chip face a parallel problem -- how to rid themselves of two designing females: Widower Steve is introduced to attractive and eligible Pamela MacLish, and is pursued by her because she wouldn't mind being the new Mrs. Douglas. Steve's youngest son Chip, aged eight, has similar problems with his classmate Dorine Peters, who would love to be his steady girlfriend. Pamela decides to call upon Steve with some leftover cake from their dinner, only to be met with a rambunctious houseful of children. Michael O'Casey, Steve's father in law, affectionately known as 'Bub' attends to the household chores. The eldest son Mike, aged eighteen and named after his Grandfather, is talking on the telephone, while middle son Robbie, aged fourteen, plays with the family's shaggy dog, known as Tramp. Before long Steve is accompanying Pamela and Chip to Chip's grade school dance. Chip takes it upon himself to give his father some sonly advice. Me

The Annual School ragdrive starts Chip off on a scavenger hunt of the neighbourhood. Everytime Miss Pitts looks out the window she sees strange happenings at the Douglas household. She sees Bub outdoors waving a bottle that looks like whiskey,and later, Robbie carrying in a dummy that she thinks is Bub smashed to the nines. Later she goes over to talk to Steve about her concerns, and sees Chip in his bedroom hitting the dummy and when it accidentally falls out of the upstairs window, she faints on the sidewalk.

When Bub steps on the toes of each grandson in turn, Steve is about to rebuke him when the household returns to normal once again. Being chief cook, dishwasher and housekeeper to three boys is not fun for a grandfather as Bub soon finds out.

A Missile launch, sleeping in and Daylight Saving make for an interesting Monday morning. The Douglas household is a chaotic affair of lost indian arrow heads for Chip's turn in show and tell at School, Robbie's missing trumpet and some important lost plans of Steve's that Mike has nearly burned in the incinerator.

When Mike and Robbie cross swords over a blonde schoolgirl, the issue widens until the whole family is involved in the argument. But it is difficult for Steve to teach his sons that violence solves nothing with a pugnacious father-in-law around.

Steve's theory that 'life is just a small series of adjustments' is put to the test in just one day's discovered doings. Steve must meet with a top Air Force General to discuss plans for a rocket design, and in the process, he must borrow Mike's car, but gets a flat tire and must take the bus home.

Steve is enamored of his new business associate, an attractive woman who is strictly business. He is tempted to mix business with pleasure but finds that she thinks only about the job at hand and doesn't have any plans to expand her love life, despite this romantic interlude.

Thanksgiving Day's turkey dinner is threatened when the electricity is short-circuited throughout the neighborhood. Chip decides to bring along his Indian friend as his sole guest much to the annoyance of his brothers who say he is a bum who lives near the railway tracks in a rundown old shack.

Feeling left out when Mike and Robbie decide to go camping at Gunman's Gulch, a lonely Chip uses a raft his brothers helped make in the backyard, on which he and Steve spend a night, pretending to float down the Mississippi. They are accidentally locked out when it begins to rain. Steve begins to worry when he wakes up from a nap and thinks it is way past 4am in the morning and thinks that Bub has not yet returned from his pinochle game.

TV Star George Gobel is invited to dinner by Bub, who forgets to tell his son-in-law Steve who returns from an out of town business trip and arrives home late at night. He tiptoes around the house only to find a strange man occupying his bed.

Robbie is baffled when his girlfriend rejects the excitement of his new motor in favor of standard feminine frills. He tries to win her over by telling the boys on the football team that no girls are allowed, knowing this will upset her as she is considered one of the guys.

The boys want a raise in their allowance, but Steve tells them that they are spending money recklessly and not doing their chores. Bub has been picking up the slack and doing their work for them. Everyone has bad dreams that night.

Mike and the girl next door arouse the suspicions of Steve and Bub when secrets are exchanged and the two are seen leaving with suitcases. Meanwhile, Robbie is on a clock salvaging attempt to find historic clocks after he gets into a spot of bother with his teacher.

Constant comparison to his brother, Mike, leaves Robbie feeling inferior and angry—and their father has to face the consequences as Robbie and Mike are about to come to blows when Steve shows up just in the nick of time from work.

When Bub is suddenly called out of town, Steve seeks an agency to get temporary help—unaware that he may be recruiting a wife. With his older brothers passing the buck, Chip accidentally rings Domestic Bliss, Inc. - a marriage seeking department who send out a woman inspector right away.

When Steve invites his second cousin Selena to come and visit, Bub gets the strange impression that he is being neglected and isn't really needed. He decides to take up the offer of managing a movie theater in Plainview, and nothing the boys say or do can make him change his mind.

Mike prepares for the transition from high school to college and the question of joining a fraternity is one that complicates his life considerably. When Mike and Jean attend a party as prospective applicants, he later finds out the they have been dropped from the waiting list and suddenly the cold war turns pretty hot.

Chip falls foul of the school bully who isn't interested in fighting with him. Steve soon realises that Chip is deliberately provoking the boy each day in the school yard to prove a point, and feels the boy must must solve his own problems even though it costs him detention in the Principal's office.

Steve's ever efficient sister arrives for a visit, and immediately changes and complicates the entire Douglas household. The challenging aspect to the whole deal is a decision that Harriet soon regrets, especially once Steve returns home from his business trip.

When Robbie Douglas sees his new friend's home he is envious of what he thinks is really the perfect teenage home and becomes almost as envious as Hank is of the turbulent, happy-go-lucky Douglas household.

Mike Douglas and the family mongrel Tramp keep disappearing at night, and Jean becomes increasingly suspicious, unaware that Mike and his friend Tim are building her a hi-fi set for her upcoming Birthday.

On a dark night when Steve is away, Robbie and his date are frightened by a man in a trench coat. It all happens when Robbie is seen putting on the hubcap of his next door neighbour. Steve isn't too concerned when he hears about the incident as he thinks it all stems from Robbie's steady diet of spy and mystery stories.

Chip begins to think it would be great to be an older brother, so he wishes for a little sister. After the new Hawkins family move into the vacant house across the street, a wild sequence of events results from an improbable case of mistaken identity -- an infant is somehow confused with a leg of lamb left in the boot of Steve's station wagon.

Chip brags to his new playmate that his genius brother Robbie can fix almost anything. Soon Robbie is repairing a Grand Piano and has five minutes to have it fixed before the boy's mother comes in and wants to practise a new tune on it.

With Steve away in Seattle on a business trip, the Douglas household's version of man's best friend has been known to drag home anything he can get his jaws into. This time Tramp slinks in with a large stick of dynamite that has somewhere and somehow survived since the end of the Second World War.

Unaware of each other's problems, Steve and Robbie engage in what seem to be widely varied projects. Robbie is trying to construct a race kart and Steve is in a rush to help a missile manufacturer get his project off the launch pad in a race to beat a rival company.

Robbie and Mike want some extra pocket money but Steve tells them that they will have to earn it by themselves. The boys ask their neighbours if they could paint their front fence and before long several neighbors pitch in together to help restore the yard to its former glory.

Robbie can't seem to arouse the interest of the affairs of the heart with his classmate Maribel Quinby. So with the help of his best friend Hank Ferguson, he proceeds to try and get her attention by noting the theatrical method of approach that his history teacher employs to make a dull subject interesting.

Chip is so discouraged by his batting slump that he quits the baseball team. After his brothers encourage him to return, one of the parents, a volunteer umpire, calls in sick and Steve is asked to substitute. Chip thinks this will be the perfect opportunity to become the team hero.

Malcolm, a frog that Chip has captured for a school project is the focus of all eyes in the Douglas home. Bub discerns a marked resemblance to his his Uncle Clancey in Malcolm's face. Further evaluation of its character becomes quite difficult when he leaps out of sight.

Robbie's new girlfriend, lives in refined and elegant style, causing Robbie to turn a critical eye on his own home life. To impress her he tells her he really digs the classics, but in actual fact he doesn't know the difference between Puccini and Presley.

Bub sets out to find the mysterious person who sent him an old saddle... C.O.D.

Its final exam time and Mike and his girlfriend Jean have thought up a test of their own - to try the strength of their affection by not seeing each other the week before school has its graduation ceremonies.

Mr. Pearson's idea of a quiet drive in the country with his wife is altered by a station-wagon load of Douglases. Meanwhile Robbie is trying to avoid the clutches of a girl named Mary Lou.

Mike Douglas gets a Summer job with the Forestry Service and he thinks its going to be a barrel of fun until he learns that he's expected to do a real man's job. When his boss is stranded down at the creek and a wild storm brews up, Mike spends a harrowing time trying to stay calm.