Megan throws Don a surprise birthday party, the war between Pete Campbell and Roger Sterling intensifies, and new mother Joan begins to wonder if she still has a job when she's ready to come back.

Megan is hurt by Don's negative response to the surprise party, Lane finds a missing wallet in a cab, Joan makes an unexpected visit to the office, and Pete makes a play for a bigger office.

Betty discovers that she has a tumor, Peggy interviews an obnoxious young copywriter for a job, the firm tries to get the Mohawk Airlines account back, and Don and Harry try to court The Rolling Stones to record a commercial.

Don runs into someone from his past. Joan makes a decision, and Roger gives Peggy extra work.

While Lane needs some help closing with a potential new client, Peter begins to crack under the pressure of both his home life and work life.

A peaceful hotel getaway ends in disaster for Don and Megan, an LSD trip could have a disastrous effect on Roger's marriage, and Peggy loses her cool after an unsuccessful pitch meeting.

Don gets a visit from the in-laws and his children just as he's about to receive a prestigious award and tries to save the Heinz account. Meanwhile, Peggy and her boyfriend take the next step in their relationship.

Megan convinces Don that she should give up her job at the firm so that she can pursue a career on Broadway, while Peter has a fling with an acquaintance's wife.

A depressed Betty tries to make things uncomfortable for Don and Megan, Roger tries to take out some secret weapons for a meeting with a prospective Jewish client, and Don makes a snap judgment that angers the creative department.

Lane searches for a way to get rid of a sizable debt, the firm prepares to pull out all the stops when it gets a second chance to land Jaguar as a client, and Don tries to comfort Joan when she reaches her breaking point.

Peter asks Joan to make an unspeakable sacrifice to help secure the Jaguar account, Peggy prepares to make a drastic move in response to Don's treatment, and Megan's acting career begins to create tension with her and Don.

Lane's entire world comes crashing down after getting busted for forging Don's signature on a check, and Sally experiences an awkward rite of passage while spending the weekend with the Drapers.

As the partners consider expanding the office space, Don begins seeing ghosts and gets a request to advance Megan's acting career. Meanwhile, Peter's affair comes to a disappointing end, and Megan's mom briefly reunites with Roger.