Last night's Mad Men, "The Better Half," was an episode about the difference between perception and reality — inspired, of all things, by the difference between butter and margarine.

"Price is irrelevant, because the question is, 'Does it taste better than butter?'" Don says at the start of the episode. "Butter is fresh. Margarine is indestructible." Mad Men was originally sold on the narrative that its lead character was indestructible, and many of the show's characters still believe it. But it's clear in last night's episode, as it has been all season, that Don is in a tailspin, and he seems neither capable nor interested in pulling out of it before the crash.

According to Harry, the outside perception is that the newly formed SCDP-CGC is the advertising version of the '27 Yankees, which featured one of the most legendary batting lineups in history — even though the inside of the firm is a mess. That same division between what people seem to be and what they actually are also extends to the show's characters. Pete Campbell, who's done more than Sterling, Cooper, Draper, or Pryce to keep the original firm afloat, is deemed by Duck Phillips to be an insufficient player. Roger, a man in his 60s, is compared to a four-year-old. And despite the apparent stability of her relationship with Henry — and her utter disdain for Don at the end of last week's episode — Betty pulls her ex-husband into her cabin at Bobby's camp for a one-night stand.

But Don and Betty's tryst wasn't the only big relationship moment in "The Better Half," which was absolutely packed with romantic entanglements. Joan has started dating Bob Benson, the alarmingly chipper new recruit at SCDP-CGC — and aside from a brief and unexpected visit from baby daddy Roger Sterling — things seem to be going well. Unfortunately, the same isn't true for Peggy and Abe, the long-suffering couple who finally break up in "The Better Half" after Peggy accidentally stabs him in the middle of the night. "Your activities are offensive to my every waking moment. I'm sorry, but you'll always be the enemy," says Abe as they take an ambulance to the hospital. So yes, it's likely that their breakup will turn out to be a permanent one.

But then again, stranger things have happened, and do happen in "The Better Half," as Betty leaves the door open — both literally and figuratively — for a one-night stand with Don, who takes her up on the offer.

Once again, Don is on the outside, looking in at the happiness that Betty has. It wasn't too long ago that he would have been the one in Henry's chair.

We know, of course, that any recollection Don has of happier times with Betty is mostly an illusion. Betty is just the latest in a string of women in Mad Men who have skewered Don with judgments and prophecies — think Wendy, who told Don that his heart was broken last week, or Dr. Faye Miller, who correctly predicted that Don would be remarried within a year at the start of season four. But Betty's analysis of Don and Megan's relationship may be the most damning we've heard. "That poor girl," says Betty as she and Don lie in bed together. "She doesn't know that loving you is the worst way to get to you."

Betty may not be around to see most of it, but she's right; things are looking pretty dicey at the Draper household. After unsuccessfully appealing to Arlene for help and support — an action that Arlene takes as an invitation to come on to Megan again — it's clear just how isolated Megan really is. "I missed you," says Don as he returns, but he's lying. "Well, I miss you all the time," she says, almost drowned out by the sirens below them.

It's a fitting interruption to the scene. "The Better Half" offered plenty of emergencies — several of them literal — but the crisis Mad Men is really interested in is the implosion of Don Draper's latest marriage, which seems, despite his reassurances, to be on the horizon. "I don't know where you've gone, but I'm here," says Megan. "I keep trying to make things the way they used to be, but I don't know how. And maybe it's stupid or young to think like that, but something has to change." Don agrees, but offers no suggestion as to how anything can change between them — and given that Mad Men's sixth season has been entirely predicated on the idea that Don can't change, it's hard to imagine anything but more pain in their future.

Read more Mad Men recaps:
* Mad Men recap: 'The Crash'
* Mad Men recap: Fifty Shades of Draper
* Mad Men recap: 'For Immediate Release'
* Mad Men recap: 'The Flood'
* Mad Men recap: To have and to hold
* Mad Men recap: Sex, lies, and a ketchup account
* Mad Men premiere recap: Death and 'The Doorway'