Spoilers are funny things.

It’s tricky enough to write about a show without delving into the plot mechanics, and even more so when you can’t even touch upon certain aspects of the plot in even a cursory way. But that’s always been the case with AMC’s Mad Men, which returns for its sixth—and penultimate—season on Sunday at 9 p.m.

Creator Matthew Weiner wants to ensure that even the most quotidian of details about the plot remain concealed. Members of the press who received an advance copy of the two-hour season premiere were instructed not to reveal several elements about the new season, a detailed list of plot points that are considered verboten. Those restrictions make writing about Mad Men’s beautiful and bravura Season 6 opener (“The Doorway”)—gorgeously written by Weiner and directed by Scott Hornbacher—a minefield of potential missteps, but fortunately not entirely impossible to navigate.

The title is a clue to what is at play within Mad Men’s ambitious sixth season. Doorways are, of course, both a means of entrance and exit, and how you see this portal depends a lot on your state of mind at the time. Are we coming or going? Or, in an existential sense, aren’t we all always coming and going, the world forever on that inexorable loop of birth and death? Issues of mortality carry over from the brilliant (if somewhat polarizing) fifth season, which saw all manner of death imagery swirl around Don Draper (Jon Hamm) and the staffers at Madison Avenue ad agency Sterling Cooper Draper Pryce. This emphasis on the transitory nature of life—embodied in last season’s suicide of Lane Pryce (Jared Harris)—looms still over Season 6.

If we are forever on that trajectory—from the womb to the grave—what matters most is perhaps how we spend the time we have, and what we make of ourselves. But for Don Draper, the quick-change chameleon ad man, identity is something fluid and fraught. An admonition to “be yourself” results in nothing but confusion. Who is Don, really? It’s a question that has been posed time and time again throughout the first five seasons of Mad Men, and one that he often answers through the relationships with the women in his life: first wife Betty (January Jones), daughter Sally (Kiernan Shipka), and his latest wife, actress Megan (Jessica Paré). Don isn’t so much a person as a reflection, a shadow, the wet ring left on a bar by a glass of Scotch.

The darkness that physically consumed Don at the end of Season 5—a sequence that Weiner told me would be vitally important to unlocking the season opener—is still in play here. There’s a sense of isolation around Don, a sense that he’s cloistered himself and his heart in many ways. The first eight minutes of the episode, in fact, feature Don in a perpetual state of silence, unspeaking, disconnected, somewhere else entirely. For a man who relies on his words, Don is unable to articulate the spiritual experience he encounters in Hawaii, a place that approximates Paradise for the taciturn ad man.

What Don needs is a guide, his own Virgil, or at least “10,000 volts of electricity,” a jolt to wake him from his silent slumber. His desperation to feel something—an emptiness that is reflected in several other characters here—displays the true void at his center. (And interestingly, motifs of faith crop up throughout the episode as several players attempt to find some sort of compass by which to travel.) Does he choose a path of darkness, or the “hot, tropical sunshine”? Does he pick up yet another identity, a cast-off item left on a barstool?

An ad campaign becomes a jumping off point for Don’s own mental state, revealing an aura of uncertainty surrounding so many at this point in American history. In fact, several characters look to shed their skin, to remake themselves, to find a leeward point from which to leap. In many ways, this is not a locus that is inhabited solely by Don within the narrative, but by several characters looking for a transformative experience. A cigarette lighter contains a message of responsibility and regret; a shoeshine kit a powerful memento mori.

That very inevitability crops up throughout “The Doorway,” numerous comings and goings both literal and figurative. A knock at the door brings with it the possibility of both good news and bad. Hamm once again delivers a stunning performance here, last season’s question posed to him—“Are you alone?”—a palpable weight that plays out in numerous and unexpected ways.

In episodes like Season 4’s “The Suitcase,” Mad Men often played out as a two-hander between Hamm’s Don and Elisabeth Moss’s Peggy Olsen, who went their separate ways toward the end of last season. If the people who truly know us leave our lives, are we then alone? It remains to be seen whether Don and Peggy will cross paths down the line, but—without spoiling anything—I can say that Peggy has most definitely been transformed by her time with Don and his tutelage. When we meet up again with Peggy in Season 6, she’s a far different woman than that naive girl at the start of the series. A demand for fresh coffee, delivered with both a grimace and a surprising insouciance, is one indication of just how far she’s come, now that Peggy is the one holding the power.

Unlike “The Suitcase,” however, “The Doorway” is an ensemble affair, with no less than four separate stories playing out over the course of the episode, as Don, Peggy, Roger (John Slattery), and Betty engage in their own metaphorical searches. What they represent is a searing and honest exploration of the conflict between how we perceive the world and how the world sees us, and how the dichotomy of heaven and hell depends on the beholder. The road to Paradise is fraught with peril.

There is the sense too that death is an inevitable final exit, a gateway to the unknown, though Don demands of his doorman—who suffers a near-death experience in front of him—to tell him what he saw after he died; it’s one of three collisions with mortality in the episode. Sometimes, such a brush with the mortal is a wake-up call, other times it’s an emptiness, a vast chasm of unfeeling.

Mad Men’s “The Doorway” tackles its exploration of death with a combination of grace and grit, with both the somber beauty and the very messiness of expiration on display here. (It’s not always a bright, white light; sometimes, it’s all too messy and mundane.) Which is, at its heart, one of Mad Men’s greatest strengths: the way in which it recaptures a lost time but also reflects our own contemporary mores back at us. In this respect, Weiner is both archeologist and astronaut, and Season 6 of Mad Men is no exception, a beautifully realized and dazzling re-creation of our collective past and a glimpse of the infinite and unknowable. Whether we’re coming or going doesn’t matter, in a way. What Mad Men’s “The Doorway” asks of its viewer is simply this: stay.