Aeronautical Engineer Steve Douglas and his youngest son Chip face a parallel problem -- how to rid themselves of two designing females.

The Annual School rag drive starts Chip off on a scavenger hunt of the neighbourhood. Every time the neighbor, Miss Pitts, looks out the window she sees strange happenings at the Douglas household.

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—and at the urging of his father to use his imagination, to conjure up an adventure—a lonely Chip decides to spend the night on a raft his brothers made him in the backyard.

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.

Mike has to finish the layout and write a sports article for the school paper by himself in between running in a track meet and going to a dance with Jean.

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.