Welcome to Season “X” of “Game of Thrones.”

Otherwise known as the mystery season, the secret season, or the season of winter, snow (and Snow).

Indeed, the forthcoming sixth season is the one where nobody — or at least no fan — is supposed to know much going in. As the world’s most popular TV series gets underway Sunday, April 24, at 9 p.m., HBO has essentially told viewers to believe nothing you read — including what you are about to read.

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Caveat emptor.

Now, proceed.

Without question, the sixth season launch is one of the most unusual in TV history. HBO declined to give critics review copies of the early episodes because some episodes had been posted online last season before launch. Only the president — you know him as Barack Obama, also a “GoT” fan — got copies after he requested them. The business of running the country had to wait while the business of Westeros briefly took precedence.

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What is going on here? Lots, and we’ll get to six questions (and answers) below. Foremost, fix in your mind the most salient detail, which has stoked fan interest as never before: Reliant on the five books comprising George R.R. Martin’s “A Song of Ice and Fire” over the last five seasons, “GoT” is going into the sixth without a book as guide. The next volume, “The Winds of Winter,” is still in Martin’s typewriter (so to speak).

The popular “GoT” blog, “Winter Is Coming,” sums up the current situation this way: “Book-readers and Unsullied alike are on equal footing for the first time. There are no known knowns.”

If there are no “knowns,” what then is the major unknown?

The December promotional tease closed with this, “the past is already written, the ink is already dry . . . They have no idea what is going to happen.” “They” (of course) refers to the Lannisters, Starks, Boltons, Greyjoys and all others vying for the Iron Throne but also perhaps to HBO, maybe even showrunners Dan Weiss and David Benioff. Both recently told Variety their plan was for two more shortened seasons after this, each comprising six or seven episodes. HBO wants more, but it appears no one knows quite how to get more. The follow-up to Martin’s “Winter” — “A Dream of Spring” — could be many years away. Even though the showrunners most likely know how the book saga will end, they can’t scoop Martin, either. Therefore, they have to craft their own conclusion, independent of the books. It’s a curious conundrum, possibly unprecedented in TV, but without the books as blueprints, it also forced them on a fast track to a series wrap. (And don’t worry — there will likely be a movie franchise someday).

Could the sixth season cover storylines from earlier books?

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That’s certainly conceivable, also another topic that has tied up the “GoT” fan community for months. Both Weiss and Benioff have long indicated they don’t want to play the “flashback” game, but they may have no choice, while another recent “GoT” tease hinted that other storylines not already covered in the series from the last two books — “A Feast for Crows” and “A Dance With Dragons” (parts of which comprised the fifth season) — might be introduced. There are further hints that Bran Stark’s (Isaac Hempstead-Wright) story — to be picked up again this season after a layover in the fifth — will time-travel the show even back before those books. But make no mistake: Most of the sixth season will consist of entirely new material.

 

What have the two major promotional online teases told us?

You’ll be stunned to learn the “GoT” faithful have reverse-engineered these to such an obsessive degree that many are now convinced they know exactly what is coming (besides winter). Keep in mind, HBO’s teases are designed to trick as well as treat. Nevertheless, a few key plot points appear reasonably clear: Humiliated last season, Cersei Lannister (Lena Headey) is plotting her revenge/comeback this season; also with revenge on her mind, Sansa Stark (Sophie Turner) has escaped the brutal Ramsay Bolton (Iwan Rheon); and, surrounded at the end of last season by thousands of hostile Dothraki khalasar (a nomadic race of warriors), Daenerys Targaryen (Emilia Clarke) has been forcibly taken to their city, Vaes Dothrak.

 

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What about Jon Snow (Kit Harington) — dead or alive?

The question that launched a million stories and online posts — all fevered, all based on pure speculation — will almost certainly be answered this season, and one part of it already has been. HBO recently in fact confirmed one single plot point: Knifed by members of the Night’s Watch at the end of last season, Jon Snow is dead. But “dead” is not always “dead” here. Indeed, fans fully expect him to return to life this season, and they are probably right — the smart money seems to be by midseason, but a late season reanimation remains a good bet, too. He is simply too popular and important a character to lose for good.

 

But (ummm) how can he come back?

As you may already know, the books have established precedence. Catelyn Stark (Michelle Fairley) was brutally slain during the Red Wedding (“The Rains of Castamere,” third season). However, she was brought back to life by Lord Beric Dondarrion in the book, “A Storm of Swords,” and renamed Lady Stoneheart. Dondarrion — himself reanimated a few times, looking a little worse for wear after each — also appeared in the series, and was played by two actors (David Michael Scott and Richard Dormer). He never got around to bringing Catelyn back, but some fans expect he might this season or next, while Stoneheart might even have a role in the return of her “bastard” son, Jon.

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Is it possible we’ve all been so busy looking at the trees of “GoT” — figuratively speaking — that we forgot to look at the forest?

Eyesight and blindness — seeing or not seeing, also hindsight and foresight — have been key themes and metaphors (borrowed mostly from Shakespeare) of both book and TV series. But few fans rarely talk about them because we are so intently focused on the many details of this gorgeous enterprise, like the forthcoming season. Yet while endlessly fussing over what might happen, it’s entirely possible we neglected to ask the right question instead:

 

What does it all mean?

Besides Shakespeare — who sometimes equated vision with wisdom — Martin once cited William Faulkner’s famed Nobel Laureate speech as one of his inspirations for “A Song of Ice and Fire.” “The young man or woman writing today has forgotten the problems of the human heart in conflict with itself,” Faulkner said back in 1950 as the Cold War was entering a deep freeze. “He writes not of love but of lust, of defeats in which nobody loses anything of value, of victories without hope and, worst of all, without pity or compassion.” Faulkner then challenged writers “to help man endure by lifting his heart, by reminding him of the courage and honor and hope and pride and compassion and pity and sacrifice which have been the glory of his past.” Years later, a famous fantasy fiction writer — followed by two TV producers — took up the challenge.

 So this much we do know: The sixth season will still be about the human heart divided against itself. And maybe -- hopefuly -- about the wisdom needed to begin mending itself, too.