Top adman Don Draper works at one of New York's most prestigious ad agencies in the 1960s and '70s, but his personal life sometimes gets in the way of his performance at the office.
Sal and Don take a business trip to Baltimore, while new financial officer Lane Pryce finds a novel way to assess the relative merits of Pete and Ken.
Betty clashes with her brother over the best way to care for their father, and Don is asked to come up with a campaign to promote the building of Madison Square .
Roger throws a party at his country club, but Don is left cold by the occasion. Joan discovers secrets about her husband, and an old college friend makes Paul uncomfortable.
Gene tries to get Betty to discuss his funeral arrangements, but she angrily refuses. Peggy decides to move to Manhattan, and Sal gets an unexpected opportunity.
Betty goes to the hospital to give birth, but experiences some strange dreams when she is placed under anaesthetic. Meanwhile, Duck tries to lure Pete and Peggy to his new firm.
Sterling Cooper's British owners unveil their plans to restructure the company, and the arrival of the dynamic Guy Mackendrick causes a commotion among the staff.
Don manages to secure the Hilton deal, but is unsettled when Connie insists he sign a contract. Betty's neighbours coax her into meeting Henry Francis one more time.
Don takes Betty along with him on a business trip to Rome, and Pete helps a neighbour's au pair when she damages a valuable dress.
Conrad Hilton becomes increasingly demanding in his dealings with Don, while Sal's position is compromised by a client's hostility toward him.
Betty stumbles across the key to Don's desk drawer - and her world is turned upside down when she discovers what he has been hiding in there.
Betty confronts Don with the evidence she has found about his past, and demands an explanation. Meanwhile, a former love of Roger's tries to find a way back into his life.
After learning about Don's past, Betty tries to figure out how she feels about him. Roger prepares for his daughter's wedding, and Pete fumes after being snubbed by Lane.
As Betty prepares to finalise the divorce, Don, Roger and Bert try to save the company after they discover their British owners are about to sell up.