Don is on the outside looking in on the forced indefinite paid leave from his job. While Ted heads back to New York for a few days, Don takes the opportunity to head to Los Angeles in part to meet with a California transformed Pete while he reunites with Megan, who is living full time there while pursuing what looks to be a promising acting career. Back in New York, Peggy avoids Ted at all cost while she learns to deal with the new "Don", Lou Avery, most specifically on the Accutron account for which she is getting consulting help from Freddie Rumsen. On top of that, ...
Don returns to work, but quickly falls off the wagon after learning that he's been assigned to Peggy. Meanwhile, Roger and his ex-wife go to a commune to rescue their daughter, who has abandoned her child.
While Lou becomes the object of ridicule for the copy writers, Don tries to get away to California after a call from his pregnant niece. Meanwhile, the new office computer drives Ginsberg to the brink of insanity.
Peggy has second thoughts about her Burger Chef campaign when Don is asked to pitch her commercial, Pete visits his wife and daughter on his trip back to New York, and Bob Benson gets some surprising news from G.M. about the account.
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 daughter, 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.