On the surface, the episode is structured around the firm's quest to land the coveted sports car account, Jaguar. "It's beautiful," Don describes, "but unreliable." We're led to think that these cars are attractive, but deeply flawed. They're superficially sound, but intrinsically damaged. So when Ginsberg pitches the Jaguar account to Don - "I kept imagining the asshole who's going to want this car. And he's probably already got a lot of beautiful things... the car is another woman. But a woman you can't have. Because they have all the qualities of a Jaguar - good looking, expensive, fast, and frankly, not practical." - is there any doubt he's talking about Joan? She's caught the eye of the Jaguar executive - the very asshole Ginsberg posits would want a Jaguar - and now she's fallen prey to a unique business proposition: spend one night with him or else Jaguar takes their business elsewhere.
Given the show's propensity to use prostitution as a metaphor for interpersonal business transactions - I'm reminded of Bobbie Barrett's threat to pull the Utz account unless Don sleeps with her in Season 2 - this method of premeditated sexual blackmailing doesn't seem foreshadowed as much as foreordained. All season long, Joan has steadily grasped at - and reached, no less - more and more power in a man's world. She's dumped her useless husband; and she's now raising her child alone. She's regained her head secretary post once again; and she's earning the respect of everyone at work. But when this Jaguar executive makes his proposal - not necessarily promising the account in exchange for one night with Joan, mind you; but merely promising that if he doesn't get what he wants, neither will Sterling Cooper Draper Price - what will Joan do?
The episode builds Joan's dilemma beautifully; but its real haymaker is the slight flashback it employs. Don goes to Joan's home to tell her this deal isn't worthwhile, "If we don't get Jaguar, so what? Who wants to be in business with people like that?" It sounds too good to be true - and it is - because soon after, we're presented with the harsh juxtaposition of Don's Jaguar presentation the following day and Joan's evening with the executive the night before. "This car, this thing, gentlemen - what price would we pay?" Don asks to the Jaguar committee as we intercut with Joan lying in bed with the Jaguar executive, "What behavior would we forgive?" Its representation of Joan is clear: for all the power she wants - whether it be wealth, security, or prestige - it still seems that women can't get anything of substantial value - in this case, defined as a 5% voting partner share in the business - without giving something up to the men in power.
But Joan's decision to sleep with the Jaguar executive cuts deeper than just business. From the first season, Joan has represented the Queen Bee, the one woman who has her finger on the pulse of the office. She knows everyone's dirty secrets; and she has more unofficial power than anyone else who works there. And yet, SCDP is still inherently a boy's club, as if all key meetings wouldn't be complete without a "Girls Keep Out" sign hanging on the door. With this move, does Joan really believe she'll be considered a partner in the firm? Will she really earn anyone's respect with everyone around her knowing just how she got that promotion? It seems that in order to justify this move, Joan was not thinking from a logical - or even pragmatic - perspective; rather, this decision was an act of disgust, a conceited response to the fact that not only is she aware that SCDP is a boy's club, but that now she knows where they hide their key.
But as the title suggests, this episode isn't only about Joan. It's also about the other woman, biding her time in the background, relegated to playing second fiddle - Peggy.
Peggy has always represented the fickle quantification and subjective valuation of women in the workplace. It wasn't long ago in season one when Peggy first stepped foot into the office, doe-eyed and innocent. The men didn't even glimpse at her before writing her off as just another secretary. But through the years, she's learned how to play the game - mercilessly, fearlessly, and independently. So upon hearing of Joan's promotion - to partner, no less! - it wasn't a surprise that Peggy would take this opportunity to give Don her notice of leave. Indeed, it wasn't long ago in the very same episode when Don went so far as to throw money in Peggy's face.
With Joan's powerplay paid off, Peggy knew SCDP had nothing more to offer her; it was time to go. Don and Peggy's farewell - that long kiss he gives her, his head bowed, his lips to her hand - was as touching a moment as I think we'll get in the entire series. It's been a long road for these two sides of the same coin; and this farewell serves as a brilliant bookend to their first meeting in the pilot episode when a naively youthful Peggy first reached out to touch Don’s hand, having learned that a handshake was the only path to power. Look how far she's come, baby.