We advertising types are a devious and fickle lot. We spend all sorts and time and money prying into people’s heads. We want to know what you love and what you fear and what you want. We need to know because we have things to sell you–some of which you never knew you wanted until we told you that you did.

So sometimes we sit you in a room with other people like you, and we pay someone to ask you questions about your life while we sit behind a two-way mirror and watch (and–let’s be honest–make fun of you). These focus groups have a whiff of science about them; after all, we call them research. But they’re completely manipulated and manipulative. We’re not doing objective field studies. We’re looking for support for what we already think about you.

A focus group among the young secretaries at Sterling Cooper Draper Pryce is the centerpiece of “The Rejected,” the fourth episode of the fourth season of Mad Men. Dr. Faye Miller, the focus group moderator, sets the tone of deception right away: she removes her wedding ring to appear to be “one of the girls” and starts the session with a comment that further ingratiates her with the group.

Don and the gang are trying to get a handle on Pond’s Cold Cream. There are two strategic messaging premises floating around the agency: Peggy’s idea that it’s all about the ritual of staring in the mirror admiring yourself, and Freddy’s idea that it’s all about snaring a husband. (Note to client types: copywriters have all the ideas.) One of the women from the steno pool breaks down over the boyfriend she lost–in her mind, because she’s not beautiful enough. Her tears trigger a chain reaction, and Allison–the secretary Don seduced a couple of episodes ago–sobs and runs out of the room. All this mind-probing has left her feeling vulnerable, and she ultimately confronts Don–

–who, clearly, doesn’t understand what she wants.

This is the point we encounter time and again in “The Rejected”: the opacity of our inner worlds. As hard as we try to understand each other, for whatever ends; as much as we want to be understood; as far as science has advanced in helping us understand what we think and why we think it; we are still mysteries to each other. We don’t know what other people are thinking, not really–whether we’ve just met them or we’ve lived with them for the better part of a century, like the elderly couple who, at the end of the episode, slam their apartment door in Don’s face before answering the question that’s been posed. Don has no choice but to retreat into his own fortress of isolation and regret.

This is an episode resonant in powerful imagery and rich in story development. Pete Campbell, of whom we’ve seen little this year, finds out he’s going to be a father the same day he’s told he’ll have to resign the Clearasil account because Pond’s views it as a conflict. Clearasil is his father-in-law’s brand. But after a lunch with former Sterling Cooper account executive Ken Cosgrove, Pete is inspired to use his father-in-law’s feelings of guilt and loyalty to make a play for the entire Vick’s Chemical account. Nice to see that our favorite junior partner is still a nasty manipulator and a user.

Peggy–past victim of Pete’s nasty manipulations–has a good story arc going, too. She falls in with a lesbian photo editor at Life, and meets a bohemian art crowd at a crazy happening at a downtown loft. She’s torn between two worlds–maybe three worlds. She wants her career, she longs to be loved, she digs the excitement.

But it’s the shot of Peggy peering through a high window into Don’s office after Allison’s meltdown that brings the episode into sharp, sad focus. They’ve spent an hour or more watching people through two-way glass; now Peggy is watching Don, still trying, without being noticed, to understand what’s going on. It’s a powerful statement about the human condition: we want desperately to know. We’ll never really know.

Don puts the cherry on the sundae and wins the plaudits of copywriters everywhere in his response when Dr. Faye tells him her preliminary findings suggest that girls just want to get married. “Hello, 1925,” he says. “You stick your finger into people’s brains, and they just start talking. Not only does it have nothing to do with what I do, it’s nobody’s business.”

Ironically, of course, it’s literally his business. But he’s also correct when he tells Dr. Faye that, in many cases, people have no idea what they want until he tells them what they want. Which is also his business.

And mine. Off to write some copy!