Steve attends a bachelor party for an older co-worker, expecting just a simple dinner. However, a dance girl was hired, and the party is raided by the police. Steve helps the girl slip out the back and things get complicated after that.
When preparing for a business trip, Steve realizes he could drive and take the time to stop at the town where he grew up. He takes the whole family on a vacation with him. He walks down memory lane, and the boys enjoy the trip.
Steve gets a letter from a woman he supposedly dated a long time ago who says she'll be in town and would like to get together. She appears to remember an awful lot about Steve including his likes and dislikes, and keeps calling him Stevie. On the other hand, try as he might, Steve does not remember her at all.
Chip and Ernie's school holds a father and son competition in the school subjects. The sons easily beat the fathers with the subjects they have been learning. A rematch is held on a local television station.
For entertainment, the family decides to play music together. Everyone has an instrument to play - except for Ernie. Uncle Charley tries to teach Ernie to play the violin, but finds out Ernie has no talent for music.
Robbie tries to earn extra money by starting a birthday cake delivery service at his college, meanwhile the family forgets Steve's own birthday. The home business goes great until it gets overwhelmed with orders, and health authorities get involved. Spoiler alert: The episode ends with a colorful cake and pie tossing fight in the Douglas' kitchen.
Robbie isn't doing well in his chemistry class and hires a tutor recommended by his professor. The tutor turns out to be an attractive older woman (Susan Oliver), and Robbie thinks he's in love, but he's concerned about the age difference. Complications arise when Robbie discovers that his tutor is actually dating his father, Steve, who is concerned about dating a younger woman.
Chip (Stanley Livingston) goes on a date with a teen movie star (Sherry Alberoni) thanks to Ernie (Barry Livingston), who had requested a photo of her as a birthday present for Chip. The studio's publicity man (Tommy Noonan) arranges to send the actress, in person, to Bryant Park, but Chip becomes disenchanted by all the attention which she is getting.
While on a business trip, Steve and a co-worker go to see a past-her-prime lounge singer (Jaye P. Morgan) with a dwindling audience. After learning that the club is letting her go, Steve invites her back to Bryant Park to learn a hipper music style from Robbie's band. When the band invites her onstage at their next gig, the kids in the audience are unenthusiastic at first, but soon dig the new singer.
Ernie learns that the person with the least experience at his father's company has been laid off - his father explains that it is unfortunate, but that is just how it goes sometimes. When Ernie discovers that he's allergic to Tramp, he decides to leave home and look for a new family to adopt him, because Tramp has been with the family longer than Ernie, so Ernie is low man on the totem pole.
Chip wants to take his girl friend from school to a party. She lives with her grandma who is old fashioned and doesn't think she should date until she's 16, so chip gets some advice from Uncle Charley that eventually works. But Chip finds that once he stirs up old memories in Grandma its not going to be easy to get out of the house.
No one believes Ernie when he says that he saw a flying saucer, so he returns to the site with his camera and takes photographs. After Steve gets them developed, he immediately takes the photos to the government where it is explained that Ernie saw a new top secret Air Force project that went awry, but Steve isn't allowed to tell Ernie any of the classified details.
A new family moves in next door to the Douglases - a widowed mother and her three children, plus "Aunt Maude". Robbie (Don Grady) and the daughter Peggy Snell (Jackie DeShannon) get along swimmingly, but the rest of the family members are at odds with their next-door-neighbor counterparts. Robbie is caught in a Romeo & Juliet romance, until he and Peggy set Shakespearean dialog into modern songs and play them for the families.
Robbie and Steve nearly forget that trout season starts on Saturday which means it's time for their annual fishing trip together. One problem: Robbie hates fishing, but is apprehensive about telling his dad, who loves it. Meanwhile, new family member Ernie is all to eager to go along, but Steve tells him his chance will come some time in the future, after Chip - who also hates fishing - gets his chance. Ernie learns that he is considered a true Douglas family member because he can wait his turn.
Ernie's friends brag about the athletic abilities of their fathers, and agree to compare sports trophies that their fathers have won. To Ernie's dismay, the only trophy he can find is for debating. The kids then decide that all the fathers will compete in a 2-mile cross country race on Saturday. Steve would rather compete in bridge or playing the saxophone, but agrees to race. It turns out that all the fathers are now out of shape, and Ernie understands when Steve lets another man win the race since his son needs the boost in self esteem more than Ernie.
Robbie has aspirations of becoming a bullfighter. He starts out by confronting a killer bull with no knowledge about the sport whatsoever. Then, after a few lessons, he tries out his skills on a farmer's pet bull, who is tame, completely harmless and disinterested.
Anticipation is high as Robbie prepares to ask the exchange student he's fallen in love with to marry him. Unfortunately, Robbie discovers that his friend popped the question the night before, and she accepted.
Chip's class has a school dance with an olden day theme. The students are to ask one of their parents to attend with them. Since Chip does not have a mother to take, he takes his father who is matched with Chip's date's mother.
Steve is dating Natalie, who has a teenage age daughter Melinda. Chip does not like Melinda as she seems pushy. He pretends to get along with her so that his father has an easier time when dating the mother.
Charley goes to Ernie's class and tells tales of his days of being a seaman. He exaggerates a bit, and the teacher falls in love with the romance of the story. She quits her job and asks Charley to marry her and travel to Pango-Pango.
To Ernie's dismay, Steve refuses to help him with his school science project. All the other kids have their parents help them and create better projects, but Ernie is the only one who ends up learning anything.
When Ernie invites a vagabond that he befriended in the park to the house for dinner, Steve decides to not pass judgment and give Ernie the chance to realize that the guy is nothing more than a freeloader.
To Steve's dismay, Robbie quits school since he has been making money hand-over-fist by working for a friend's real estate company. Robbie gets a real education when a torrential rain storm reveals that the home he is showing has hidden flaws.
Uncle Charley gets reacquainted with an old merchant marine shipmate who invites Charley along on a sea voyage. Charley wants to go, but realizes the Douglas family needs him. The family sees that Charley wants to go, so they pretend that they are fully capable of taking care of themselves.
Steve's company sends him on a business trip to Japan and includes the entire family for an all-expenses-paid vacation. Charley reminisces about his merchant marine days, and the girl he left behind in Honolulu. Charley has forgotten that she has aged quite a bit since he last saw her, and after they meet he does all he can to avoid her. Meanwhile, Robbie runs into a girl he knew back home.