Sterling Cooper celebrated its 40th anniversary this week, while Betty discovered a major secret about her husband.

The episode kicked off with Don lying to Betty about spending the night in the city, due to the Hilton account. Instead, he went to Ms. Farrell's house. These two are having an intense affair, as she clearly sees herself as more than just a sex buddy.

At the office, Don seems especially happy about the relationship himself, smiling as he bites into a piece of break Ms. Farrell baked. Kinsey is less happy because Peggy sort of showed him up in a presentation, although she really just thought faster on his feet than he did. This would take place again later in the episode, as Peggy used a saying Kinsey had uttered only moments earlier to pitch Don a great tagline for the Western Union account. Even Kinsey was openly impressed with Peggy's work. (Or angry that she stole the spotlight again.)

In other office news: the firm was planning a major party for its 40th anniversay. Don was set to give a speech and receive an award at it, much to Roger's chagrin.

Also, the British bosses informed Pryce that Sterling Cooper was up for sale again. They see an opportunity to make money off the changes they made to it, an interesting development for everyone involved. Will this be an impetus for Don to start his own company?

Back to Don's personal life: he met Ferrell's brother, a 25-year old with epilepsy. Don offered to help by driving him to a new job in Bedford, MA, but the young man had other plans. He asked Don to drop him on the side of the road because he didn't wish to be performing menial jobs his whole life. Clearly seeing a chance to help in this case (as he failed to do with his own brother), Don obeyed, but also gave the kid money and his card, telling him to call any time.

While this was taking place, Betty was finding a key in Don's pants in the laundry. It opened a drawer in his desk. She used it. Inside that drawer, she found piles of cash, as well as a shoebox. Inside the shoebox? Pictures, dog tags and documents: all from Dick Whitman's life. The main document Betty focused on what a divorce deed between Don Draper and his wife.

She doesn't know exactly what this means, but she's understandably pissed off about it. She doesn't tell Don what she has found yet, however (it looks like she had planned to, but he never came home that night), and attends the big company party with him. The episode ends with Don about to give his speech, and the camera focused on his wife. She's staring daggers at him.