This crazy series begins when Janet Wood and Chrissy Snow, two attractive women, have a going away party for their roommate, Eleanor (who we'll meet in Episode 44). While trying to find someone to share the rent with, they find party crasher Jack Tripper in their bathtub. They have their doubts at first but when they find out that Jack is the only one that can cook (by going to cooking school), they want him to stay. The hardest part of this is trying to convince the landlords, Stanley and Helen Roper, that Jack is indeed good company. Stanley doesn't like the idea of a man living with two women, knowing what can go on behind closed doors. Jack pretends he is gay so that he can have a place to live. It works, and the rest is sitcom history.

Jack is all set to move into Eleanor's room, until Chrissy's mother unexpectedly shows up. Chrissy's mom does not know that she and Janet live with a man, so she tries to keep them out of sight. Janet and Jack go to the Regal Beagle to hide out, and Mrs. Roper finds out that Jack is not really gay. She manages to keep it secret from Mr. Roper.

In order to earn tuition money, Jack takes on a variety of odd jobs, including an encyclopedia salesman and a nude model in a magazine layout.

Chrissy's new man is married, but she thinks he's single, and now her friends must prove to her the truth.

The kids and the Ropers spend Christmas together, but they would rather be at another party.

Janet made a date at the same time as her babysitting duty. She gets Jack and Chrissy to take her place as babysitters.

Because of one of Larry's tricks, Jack is in trouble. A girl calls him claiming that he might have gotten her pregnant. The girls think that Jack is the father, but actually Larry used his name when he dated her. Jack hears this and thinks that he got his recent girlfriend, Linda, pregnant.

Jack, Janet and Chrissy weeds the Ropers' backyard and they find a plant which they think is marijuana.

Janet has two tickets to see Frank Sinatra, and Chrissy and Jack fight over who gets to go with Janet.

Chrissy a thief? No way! At least that what Jack thinks when he sees her with his money.

After canceling a party the trio were holding, Helen (in disgust) leaves Stanley.

While flying, Jack gets a fear of heights and a stewardess named Vicky Bradford helps him out. They even go out for the first time, against her father's wishes. Meanwhile, Philip, the guy we met in the last episode, proposes to Janet.

Jack and Vicky are really good together, despite Mr. Bradford's objections. Janet and Philip get married in the apartment, and Jack wants Vicky to marry him as well.

When Jack proposes to Vicky, she turns him down cold. The reason is that she's afraid of marriage because it might fail like her father's did. They decide to live together. The trio finally moves out of their apartment and into their new lives: Terri is going to Hawaii to work with poor children, Janet and Philip move into their new place, and Jack moves into the apartment above the restaurant with Vicky. As they begin their new life together, Mr. Bradford comes in and tells him that he is the new landlord! With that, the spin-off series Three's a Crowd begins.