S3E13 · Shut the Door. Have a Seat.

Complete story — includes the ending

Don is informed by Connie that McCann Erickson is buying Puttnam, Powell, and Lowe, and thereby also Sterling Cooper. Before the sale of Sterling Cooper is to take effect, Don convinces Bert that they should buy the company themselves instead of being passed around by bigger entities. In need of capital, Don repairs his friendship with Roger. With Lane's assistance, Don, Bert, and Roger form a new agency, Sterling Cooper Draper Pryce, with them as equal partners; Peggy, Joan, Pete and Harry are recruited to move with them. Peggy is initially reluctant until Don finally recognizes her talents, telling her if she doesn't come along, he will spend the rest of his life trying to hire her. Betty tells Don that she is preparing to file for divorce; Don is angered to discover her relationship with Henry, and Betty threatens to reveal his secret identity if he does not consent to the divorce. Later, Don informs Betty he wants to avoid animosity, and voluntarily moves out, promising Sally and Bobby he'll never stop being their father no matter where he lives. That evening, Betty takes a plane to Reno with Henry and the baby to prepare for the divorce.