Cocaine may be a helluva drug , but when you inject an office full of advertising executives and workers with a special cocktail that felt a lot like speed, you wind up face planted on your white shag carpet. In an episode that felt accelerated and off kilter, frenetic and disjointed, The Crash was uncomfortable to watch, from another flashback to the worst childhood ever (a/k/a "let's raise little Dick Whitman in a whorehouse and see what could possibly go wrong") to the desperate hours spent inside the walls of SCDP/CGC, where otherwise sensible human beings were reduced to some combination of Lord of the Flies and Caligula.
The broad strokes were simple enough, another tight deadline by the ever demanding overlords at General Motors coincided with the death of Frank Gleason, leaving Don and the crew to pull an all-weekender trying to come up with new ideas for the GM executives to shoot down. For inspiration, Jim Cutler calls in his own personal Dr. Feelgood, who doses the crowd with enough amphetamines to keep them running for 48 hours strong. And while Peggy, Stan, Ginzo and the new kids from CGC scramble, babbling incoherently in the euphoria of their high, Don is grappling with his very own advertising pitch to Sylvia, who he simply cannot let go of. In his mania, Don is incapable of coherence. His kids are visiting for the weekend but he cannot be bothered to see them; his wife is going out without him, but his focus in solely on coming up with the perfect "pitch" that will convince Sylvia to take him back.
When Frank Gleason's daughter appears in the full bloom of hippiedom, I Ching in hand, clad in batik print flowing dress, she tells Don that he asked her "does someone love me" but that does not make Don exceptional - according to her, everyone asks that question. But in Don's case, we know that is a question for which he fears the answer - "no." Indeed, the only person who ever truly knew him is long dead.  Instead, the window is pulled back a little more to Don's wretched childhood where Aimee, one of the prostitutes he co-habitates with, deflowers him after nursing him back to health after he takes a high fever. She is quickly dismissed by "rooster" Uncle Mac  and Don takes a beating from Abigail for cavorting with the young blonde woman. That Don connects this episode to what he is experiencing with Sylvia is curious, particularly in light of the old oatmeal campaign that used the tag line "because you know what he needs" he ends up focusing on as the way to get Sylvia back.
Don's speed high causes him to sweat and become ever more disjointed in his thinking. Meanwhile, drugs cannot mask Stan Rizzo's pain - his cousin, who we met briefly at the beginning of Season 5,  is killed in Vietnam and when he tries to turn his sorrow into a grope session with Peggy, she demurs, advising him that masking his pain with drugs and sex will do him no good. Over on Park Avenue, Sally, who was introduced to the numbing effect of Seconal by Grandma Pauline,  stumbles on a kindly old woman who introduces herself as Grandma Ida but turns out to be a thief who has entered the Draper's penthouse apartment from an unlocked door. Although Sally has the presence of mind to call the police, "Ida" intercepts the call and makes a hasty retreat, presumably with all four of Don's watches in her satchel. When Don returns home, utterly wired and exhausted by his weekend bender, his family, both old and new, are there to greet him with the news of the burglary, with Betty twisting several knives into Don's back for his poor parenting.
Indeed, this "B" story had the most ominous overtones and was the episode at its most claustrophobic. Its insularity was amplified by the rest of the storyline, which seemed to speed up and careen under the influence of drugs and desperation, but Ida's superficial pleasantry toward Sally was tissue thin and the hint of foreboding and violence that was communicated through her words and deeds gave these scenes a menacing aspect that only reinforced the hour's ominous vibration.
Drugs have played a role on Mad Men since Season 3  but while their use (particularly marijuana) has grown since then, The Crash exposed the less salutary effects of mind altering substances. Instead of using LSD to commune with a loved one  or marijuana to get involved in some anonymous movie theater hanky panky , the Dr. Feelgood shot exposed raw nerves, anxiety and hyperactivity that is not sustainable, much less preferable even in small doses. The collective fugue produced a lot of gibberish masquerading as good ideas, but only served to allow those who were under the drug's spell a brief respite from the pain they felt in their own lives. Last night, recreational drug use went from being portrayed as ethereal and escapist to edgy and ugly.
But like so many of the narrative constructs that have been used this season that nodded to seasons past , just when Don hits rock bottom, in this case, coming home wired and ranting to a room of his first and second families and a police officer before fainting from exhaustion, the next morning, it is as if nothing has happened. He sees Sylvia in the elevator, barely exchanges pleasantries, and doesn't even pay her the courtesy of allowing her to exit first when the doors open - he simply powers past her. At the office, he makes up with Sally over the phone by taking responsibility for leaving the side door to the apartment open and then tells his partners, both new and old, that he's out of the business of being led around by the nose by the client, even one as exalted as General Motors.
To me, the end of The Crash carries on this season's echoing theme. The closest parallels are Season 4, where Don hits a nadir upon learning of Anna's death, causing Peggy to look at him with despair and ask him "how much longer are you going to do this" (referring to his excessive drinking). There, once Don experiences the catharsis of learning of Anna's passing and affirmation of Peggy's place beside him as emotional ballast, he appears the next morning in a freshly pressed suit and tie, new idea in hand for Samsonite and a request that his door be left open.  Last season, Don was drifting aimlessly and in no particular creative direction until he realized he was punching below his weight in fighting pitch skirmishes with Ginsberg and instead turned his sights on mega-accounts, landing, as we now know, Dow Chemical and Jaguar. 
Indeed, if you dig deeper into the show's history, Don is always <this close> to having things fall apart for him entirely before transmogrifying into the next iteration of himself. Back in Season 1, he was ready to flee New York in the face of Pete's blackmail threat before confronting him head on.  The following season, after his affair with Bobbi Barrett is exposed, Don does flee to California, fully accepting he has ruined his (and his family's life) but returns home after cleansing himself in the Pacific Ocean.  In Season 3, he learns of Betty's connection with Henry Francis and, in a drunken rage, attacks her. The next day, he's opening his life to the new Sterling Cooper Draper Pryce firm and acceding to Betty's request that he allow her to divorce him. 
The experiences that brought Don his swag back last night were consistent with this leitmotif, and were of a piece with what one might call Don's "Falling Man Syndrome." Matt Weiner makes this obvious literally from the moment the show's credits begin running - as everything collapses around an animated version of Don, and he descends, inexorably toward a crash; but when the curtain rises, he's perfectly coiffed, cigarette in hand, firmly on top of his game. Last night, Don Draper shed yet another skin, revealing nothing but the same impeccable surface that guides him through life.
2. The Suitcase, Season 4, Episode 7.
3. Mac's actions make one question why Don once referred to Mac as one of the few people who was nice to him while he was growing up. The Gypsy and The Hobo, Season 3, Episode 11.
4. A Little Kiss Part II, Season 5, Episode 2.
5. Mystery Date, Season 5, Episode 4.
6. My Old Kentucky Home, Season 3, Episode 3.
7. Far Away Places, Season 5, Episode 6.
9. Don's attempted assertion of dominance over Ted echoed a similar stunt he pulled on Roger in Season 1. Man With A Plan, Season 6, Episode 7; Red In The Face, Season 1, Episode 5. The agency losing two large clients simultaneously (Jaguar and Vick's Chemical) mimicked a similar story line from Season 4 (North American Aviation and Lucky Strike). For Immediate Release, Season 6, Episode 6. Hands and Knees, Season 4, Episode 10.
10. The Suitcase, supra.
11. Commissions and Fees, Season 5, Episode 12, The Other Woman, Season 5, Episode 11. And yes, it is a fair point to say that it was Joan, not Don that truly carried the day with Jaguar.
12. Nixon vs. Kennedy, Season 1, Episode 12. It is also worth noting that Bert gave Don his blessing to fire Pete and Don did not do so. A decision that began bonding the two in ways that would impact them both (and the firm) for years to come.
13. The Mountain King, Season 2, Episode 12.
14. Shut the Door, Have A Seat. Season 3, Episode 13.