Don and Betty Draper have an argument when it becomes apparent that he doesn't want to spend Thanksgiving with her family and she plans on going only with the children. He also learns some information about his brother Adam. Pete Campbell confirms that he has landed an account from his father-in-law for a new skin care product called Clearasil. He objects however when Don gives the account to Peggy Olson, whom he has just promoted to junior copywriter. Peggy proves her mettle in auditions for the weight loss device but later is feeling unwell and goes to the hospital where she is given some shocking news. Don comes up with a brilliant presentation for Kodak on a new wheel-like storage device for a slide projector that he dubs The Carousel.

On Valentine's Day, the staff of the Sterling Cooper Advertising Agency is hustling and checking out the newest office equipment. Don and Duck clash over an account, and Betty hears from an old friend.

Betty becomes suspicious that Don is having an affair after her conversation with Jimmy Barrett, Joan helps out in the television department, and Peggy helps the church with a dance flyer.

Don checks in to a hotel after his separation from Betty. Back at the office, he is forced to get rid of Freddy against his will because of his drinking problem.

Don and Betty try to keep up appearances as they go to Betty's parents after her dad has a stroke. Peter has a long-dreaded meeting with his mother before he and Kinsey leave for a convention in Los Angeles.

Under the backdrop of the Cuban Missile Crisis, Don returns to New York just as Betty finds out that she is pregnant. Meanwhile, everybody at Sterling Cooper contemplates their futures as news of the merger slowly leaks out.

Roger Sterling throws an expensive party with his new wife, Joan throws a dinner party, Peggy and Paul get stoned while working on an ad campaign, and Don's daughter Sally steals money from her grandpa.

Don and Betty renew their love affair while on a business trip to Rome, while Peter has a bout of infidelity with an au pair in his building while his wife is away.

Betty tries to meet with Henry Francis again, while Don steps up his pursuit of his daughter's former teacher. At the office, Don disappoints Conrad Hilton and is forced by a client to fire Salvatore over an unwelcome advance.

As Sterling Cooper prepares for its 40th anniversary party, the bosses in London drop a bombshell to Lane. Miss Farrell's troubled brother pays a visit to her and Don, and Betty stumbles onto her husband's secrets.

On the weekend of the John F. Kennedy assassination, Pete finds out that he lost the promotion to Cosgrove, Roger Sterling's daughter's wedding goes off as planned, and Betty musters up the courage to respond to Don's confessions.

With another sale on the horizon, Sterling, Cooper, and Draper convince Lane Pryce to fire them and then join them as they start up a new advertising firm. At home, Betty follows through with her plans to divorce Don.

Freddy returns with a valuable new client, the firm reluctantly throws a Christmas party for its most important client, and Don prepares for his first Christmas away from his children.

Don is forced to compete with a cocky upstart rival for a potential account with Honda motorcycles, but Roger's prejudice causes unexpected problems. Meanwhile Betty considers a psychiatrist for Sally because of her behavior.

Don takes the kids to California and comes back with a surprise announcement. Meanwhile, Betty fires the kids' nanny before they move out of the old house over one questionable incident, and Peggy gets a shot at a new account.