In the season 10 opener, Rob (Don Grady), Katie (Tina Cole) and the triplets have moved into their own place. Katie feels that Steve (Fred MacMurray) needs a woman in his life, so she arranges a blind date, Millicent Sawyer (Elaine Devry), for him. Meanwhile, Ernie (Barry Livingston) has a problem in school so his dad has to meet with his teacher, Barbara Harper (Beverly Garland). Rob and Katie are worried how to break it to Steve that his blind date, Millicent, isn't interested in him, but Steve has already become smitten with Ernie's teacher, Barbara.
Steve's romance with Barbara continues and despite his father's efforts not to recommend him (to avoid the appearance of nepotism), Robbie is offered a job as a structural engineer at his father's firm. He tries to talk it over with his father, who is head over heels in a very engrossing friendship and cannot be reached.
Steve (Fred MacMurray) has bought a ring and is ready to propose to Barbara Harper (Beverly Garland). After making sure his family approves, he tries to find the right moment to pop the question to an unsuspecting Barbara, but the evening is filled with interruptions and complications which lead to a proposal that was not quite how Steve had planned it.
Now that Steve (Fred MacMurray) and Barbara (Beverly Garland) are engaged, they just have to learn to adjust to each other's families. Barbara's daughter, Dodie (Dawn Lyn), is not so sure she wants to share her mother.
Steve and Barbara plan their wedding to take place in two weeks. She wants a large wedding with a lot of family and friends. Steve is thinking of a simple wedding at the office of a justice of the peace..
It's Steve and Barbara's wedding day. Not wanting a repeat of what happened before Rob's wedding, the Douglas clan awakes very early and gets dressed, then everyone goes back to sleep. Tramp runs off again and arrives at the wedding as before.
Steve and Barbara arrive in a quaint village in Mexico which Steve had previously visited on a fishing trip. They expect to find the same quiet place Steve remembers and have the place virtually to themselves. They are surprised to find the village has been "put on the map" by a travel magazine and the obscure little hotel, whose name has changed from Moon Hotel to Honeymoon Hotel, is filled to capacity with young newlyweds. The Douglases are continually put upon by the young couples around them for help with everything from homesickness, to settling quarrels to ...
Katie (Tina Cole) tells Charley (William Demarest) that he has to be more respectful and polite with a new woman in the house. When Steve (Fred MacMurray) and Barbara (Beverly Garland) arrive back home from their honeymoon, both are puzzled by the change in Charley's personality.
Katie (Tina Cole) finds a few gray hairs on her head and tells Robbie (Don Grady) they have to plan for their retirement and set up their wills; Dodie (Dawn Lyn) is worried about going from the first grade to the second grade.
The women in the family seem to have a way of getting the men to do the things they want. When Steve has to take part in a play at Dodie's school, Robbie thinks it shows that women are born with the skill.
Rob gets invited to an old friend's wedding back in Bryant Park and takes Katie with him, hoping to introduce her to other people he knew as well. Much to his surprise, virtually no one else remembers him.
Barbara feels like a guest in the house when she realizes the boys still go to their father for everything. She is never included. Then, she has to go to school to see Chip's teacher when he is accused of cheating on a test.
Both Steve & Robbie have been working long hours at work. Their wives feel sorry for them since they come home tired at the end of each day. One day, Barbara & Katie decide to surprise them at work, but find them partying instead of working
It's school problems for everyone. Barbara becomes a substitute teacher for Chip's class, and he is the smartest student. Ernie is followed by Beatrice (Victoria Paige Meyerink), one of Dodie's friends from school with a case of puppy love.