Don is oddly drawn to a diner waitress as he learns about the loss of an old acquaintance, Peggy and Joan are disrespected by a chauvinistic client, and Cosgrove is in for big changes after his biggest business connection retires.
While Megan comes to New York with her mother and sister to collect her belongings, Don has a romance with the waitress. Meanwhile, Peggy and Stan work with a famous photographer on a commercial shoot.
Don decides to sell his apartment, Joan stumbles into a relationship while on a trip to Los Angeles, Glen tells Betty and Sally that he is going to Vietnam, and a copywriter gets in trouble for his rude behavior to a client.
The partners discover that the firm is losing its independence and there's nothing they can do about it. Peggy is not sure if she wants to come along. Meanwhile, Pete and Trudy have trouble getting their daughter into private school.
Don is stuck in Oklahoma after his car breaks down. Betty discovers that she is not in good health. Pete gets an unexpected job offer that could enable him to get his life with Trudy and his daughter back.
Don's journey ends in California with Anna's niece, Stephanie, where he contemplates his future. Roger decides to marry Megan's mother, Marie. Joan has a business proposition for Peggy, who is coming to terms with her feelings for Stan.