SPOILER ALERT

It ended, as we knew it must, with Don finding himself in California, Peggy finding happiness and Joan finding herself in charge. That might sound way too much like Matthew Weiner had tied everything up in neat bows, and maybe he was trying a little too hard to give us what we all secretly wanted, but there was a coda that made it all seem right. It made the ending – Don's ending, especially – seem like the real thing. And not necessarily in a good way.

It started with him racing at speed across what looked like snow but was in fact salt. In his march back through time, here was Don the boy racer, trying to help a couple of young guns set a speed record. Not for the first time, we had a premonition of his death. "I got a hell of a shake around 130," he tells the young mechanics before casting a longing, if rather wary, eye over the car. Death, be my mistress.

Back in New York, Roger is having a frank talk with Meredith (Stephanie Drake), Don's secretary. He's not coming back, so you'll have to go.

"Is he dead," she asks. No, says Roger. "Well I hope he's in a better place," she says.

"He's not dead," snaps Roger. "Stop saying that."

"There are a lot of better places than here," she says, and I'm more than ever convinced that she's going to evolve into that hilarious and crabby-faced TV executive from Episodes.

Peggy has been dealt out of an account she'd been working on, and maybe it's just that she's inspired by the slogan hanging on the boardroom wall – "Truth well told" – but she decides to stand up for herself even though she's the new kid on the block. She tells the truth. It's her account and she wants it back. And she wins. This is the Peggy we've known was coming since she sauntered in to McCann with those sunnies, that fag, and that print under her arm. You go, girl. You take Manhattan.

We know it's the 1970s because Joan and her real estate mogul beau Richard (Bruce Greenwood) are snorting coke. "It's everywhere in Malibu," he says, though not on the Mad Men set, we're sure. Joan likes it. "It feels like I've just been given some very good news," she says.

"You know we could live like this all the time," he says, and if this weren't the final episode you'd swear we were about to head off on some weird Boogie Nights trajectory in which Joan squanders everything because of the blow. But we're not, thankfully; Richard is talking about sharing a future together.

"Do you want to get married," Joan asks, looking half-excited, half-shocked, and all coke-frazzled. Sure, he says, if you want, but he's actually way more interested in subdividing her rather formidable assets and building some boutique apartments on them. "It seems to me your life is undeveloped property," he says. "You can turn it into anything you want. It's got a hell of a view."

That must be some good stuff they're snorting, but the seeds are sown, and Joan is soon trying to entice Peggy to join her in a new production company (well she's got a taste for cocaine, why not move into the film and TV business?), to be called Harris Olson. "You've got to have two names to make it seem real," she says.

Peggy is tempted, but Stan Rizzo (Jay R. Ferguson) is right when he points out she's never even wanted to be a producer, she just wants her name on the door. He knows her so well, even if their chief tool of mutual exploration until now has been the blazing row.

In truth, he loves her, and he tells her so.

"What did you say?"

He tells her again.

"What?"

It's as if the line has gone dead. It hasn't. It's just Peggy's brain wrestling with its greatest fear – letting someone get close – before admitting it might actually be her heart's greatest desire. She ticks off all the symptoms and confesses that it appears she loves him too. She's so rational about this headlong tilt into emotion you just know that if they have babies they're going to be raised by Dr Spock.

Don calls Sally (Kiernan Shipka) at boarding school to tell her all about his second childhood as a racing car driver. She, in turn, tells him about Betty.

Betty wants the boys to go live with Uncle William, she says; he says, don't worry, they're going to come live with me. She says no, they've got to live with Henry, they've got to stay together. He tells her "grown-ups make these decisions" – which would be fine, if he knew any – and she hangs up on him, just like Betty used to.

He calls Betty. "I'm coming home."

"You're definitely not," she says.

She talks about her preferred parenting arrangement. "This way you get to see them exactly as often as you do now, on weekends and … oh wait, Don. When was the last time you saw them?"

Ouch.

"I'm not going to waste the rest of my time arguing about this," she continues. "I want to keep things as normal as possible – and you not being here is part of that."

Double ouch.

Don is in tears, all but lost for words. "Birdy," he croaks, appealing to that old chestnut nostalgia. If only he had a Kodak Carousel to hand right now, he might be able to change her mind.

Don's journey isn't back home, to the east, though, it's west. In Los Angeles, he knocks on the door of Stephanie (Caity Lotz), the hippy niece of Anna Draper who once turned up on Megan's doorstep broke and heavily pregnant. She greets him as Dick; she knows him in ways few others do and for one horrible moment (well, several horrible moments) it looks like the Draper family relations are going to head into some very "woe is me, shame and scandal in the family" directions. Not that they've ever been anywhere else, really.

Stephanie is a mess, but not as much as he is. He's drunk, bedraggled, aimless. An altogether rather appealing package. She puts him to sleep on the couch and then takes him to a hippy retreat that offers 57 varieties of therapy, a kind of Heinz of healing.

"Where are we," he asks disdainfully.

"Be open to this," Stephanie says. "You might feel better."

"She took my money," he says of the girl who showed them in. "That's a good sign."

Back east, Roger drops in on Joan, says he's been revising his will, wants to leave a big chunk to the little man he fathered.

"Roger, this is an expensive way to mark your territory," Joan says. Now she's out of the chauvinist hellhole that was McCann, she's got her old spark back. It suits her.

He tells her he's tidying up his affairs because he's getting married.

"Well, those skirts are pretty short at McCann," Joan says.

"Nah, I met her through Megan Draper. She's old enough to be her mother. Actually, she is her mother."

"That's spectacular," says Joan, delighted, in hysterics. "What a mess."

Don calls Peggy, reverse charges, and just like Betty, she accepts. And then she explodes.

"I know you get sick of things and you run but you can come home," she tells him when she calms down a little.

"Where," he asks, and it's not rhetorical. It's all been about that, his search for home, a place where he can belong.

"Don't you want to work on Coke," asks Peggy.

"I can't," he says. "I can't get out of here. I messed everything up. I'm not the man you think I am."

"What did you ever do that was so bad," Peggy asks. Man, how long have you got?

"I broke all my vows," Don says. "I scandalised my child. I took another man's name, and made nothing of it."

"That's not true."

"I only called because I realised I never said goodbye to you."

OK. This looks like the moment we've all been half expecting and secretly fearing. Don will end it all by ending it all.

As he crumples to the ground by that payphone, you can't help remembering all the moments it might have happened but didn't. Was Matthew Weiner just waiting to get his leading man to somewhere suitably picturesque – a clifftop in Carmel, for instance – before pushing him over the edge?

It looks like Don is giving it some serious thought when a lovely earth mother-cum-angel turns up and ushers him to therapy, where a guy called Leonard takes the speaking chair and talks about how nobody notices him at work, about how when he comes home nobody notices, and when he leaves they don't notice that either. "Nobody cares that I'm gone," he says.

He's non-descript, the polar opposite of Don, and yet when he starts talking about love something happens.

"I don't even know what it is," says Leonard. "You spend your whole life thinking you're not getting it, people aren't giving it to you, then you realise they're trying and you don't even know what it is."

Leonard breaks down, and Don crosses the room, hugs him, and breaks down right along with him. Surely, this is the breakthrough, the moment Don's soul is saved.

There's just time for a quick roll call of our favourite characters before it's all over. We see Pete and family board a Lear jet, bound for their new life in Wichita. Joan is running her new production company, Holloway Harris (two names, her maiden and her married) from her apartment, having decided that any man who can only be with her if she ditches her career is no man she could ever be with. Roger and Marie are in Paris, honeymooning. Betty is in her kitchen, smoking her way to a death both ugly and dignified, while Sally washes the dishes. And Peggy is in the office, working, when Rizzo comes in and plants a kiss on her forehead. All present and accounted for.

And Don? He's in California still, at the retreat, sitting cross-legged on the lawn for the salutation to the dawn.

"The new day brings new hope," intones the guru. "The lives we've led, the lives we get to lead. A new day, new ideas, a new you. Om."

The guru rings a little bell, Don chants 'om' along with the rest of them, and a smile creeps across his face. He's found peace at last.

Or has he?

And this is Weiner's masterstroke, the moment that saves it all from some "happily ever after" that would have been a fundamental breach of faith for those of us who've come this far.

The scene cuts from beatific Don to the Real Thing Coke ad, with its "I'd like to teach the world to sing, in perfect harmony" jingle.

That famous TV commercial is masterful and manipulative, the work of some evil ad man who took the hippy dream and reduced it to one syrupy 60-second spot in the service of commerce.

Some ad man who, perhaps in a blinding moment of revelation on a lawn in California, had come to understood the desire at the heart of that dream, to understood the ache of nostalgia, the need to connect, and the way products can be substituted for people to create the illusion that whatever we are doing, we are OK.

He must have been a man a lot like Don Draper, don't you think?

Saved? I don't think so. Just refreshed.

Follow Karl Quinn on Facebook

On twitter: @karlkwin