Spoilers follow for the eighth episode of the fifth season of Game of Thrones.
The harrowing 15-minute battle sequence that ended "Hardhome" — featuring Jon Snow and the wildlings trying to escape a sudden attack by the White Walkers — occurs nowhere in George R. R. Martin’s book series.
Yet Game of Thrones showrunners David Benioff and D. B. Weiss didn’t invent it out of whole cloth for this episode. In its setting, its staging, and its ultimate impact, the sequence weaves together many disparate threads from the Wall plotline in Martin's most recent book, A Dance With Dragons.
The major difference is that Benioff and Weiss tie all these on to a massive, invented action spectacle involving a protagonist and the key threat that’s been teased since book one — something Martin has conspicuously opted against doing so far.
The huge fight sequence with the White Walkers is entirely new
The biggest change is an obvious one — the huge, special effects–heavy battle scene featuring rampaging skeletons, massacred wildlings, and Jon Snow fighting a White Walker is entirely new to book readers. Indeed, in the five volumes published so far, Jon hasn't yet fought or even seen a White Walker (or an Other, as the books call them).
In the battle, the unstoppable undead horde massacres human after human, and despite Jon killing his White Walker opponent, the human survivors end up merely fleeing rather than winning. This tone actually quite resembles a book sequence early in the third book, A Storm of Swords, when undead hordes rout the Night's Watch's ranging party at the Fist of the First Men.
The show rather botched its adaptation of that sequence, showing the approaching White Walker army at the end of season two, and then cutting ahead to the underwhelming aftermath in the first scene of season three, apparently for budget reasons. Now, the series is making up for it.
But the upshot is the same as the books: the wildlings come back to the Wall
Despite this huge change, much of Jon's plotline this episode is actually quite similar to what he does in A Dance With Dragons — he offers to let the wildlings go south of the Wall if they join forces with the Watch against the Walkers, and many of them agree to this deal.
In the books, this isn't interrupted by a bonkers battle sequence, but it does happen. Midway through A Dance With Dragons, Jon sends a captive wildling north to offer an olive branch to Tormund Giantsbane — who was not taken prisoner in the books, but rather escaped with thousands of wildlings after their failed attack on the Wall. Several chapters then pass while Jon deals with other matters. Finally, near the end of the book, Tormund and his group show up, and a similar deal is reached. (Other groups of wildlings are off on their own and don't agree.)
It’s a very different and much less action-packed way to get from point A (Jon wants to bring the wildlings back to the Wall) to point B (many of the wildlings are brought to the Wall and reach an understanding with Jon). In both cases, though, we end up in the same basic place.
We don't get to see Hardhome firsthand in the books, but similar things are happening there
Elsewhere in the books, there’s another group of wildlings (separate from Tormund's group) who fled the battle at the Wall and have ended up at Hardhome. We never see them, but Jon Snow hears about them — they’re thousands of starving refugees in desperate need of assistance, including many women and children, and are apparently being attacked by White Walkers and other "dead things."
Naturally, Jon wants to rescue them — for humanitarian reasons, because he cares about the wildling people, and because their deaths would add to the White Walkers’ "army of the dead." So he sends out a Night’s Watch party on ships to help.
But the mission doesn’t succeed, and Jon gets increasingly dire dispatches about the deteriorating situation. Some of the Night’s Watch men argue that Jon should give up, saying both that he’s sending more of his own men into certain death, and that the wildlings aren’t worth saving anyway.
Jon disagrees, and plots out an even more ambitious, large-scale rescue effort that would send much of the Night’s Watch’s strength to Hardhome. The debate over what to do about Hardhome is one element of the climax of Jon’s plotline in A Dance With Dragons. This episode's adaptation of it, particularly the ending in which many wildlings are left behind to become reanimated corpses, appropriately captures the hopelessness and despair of the books' Hardhome.
The show is revealing much more about the White Walkers
George R. R. Martin introduced the Others in the very first chapter of the first book of A Song of Ice and Fire — and has barely shown them again since. Several characters have encountered reanimated corpses, but few have met the strange, magical icy beings who seem to be controlling them. Even five books in, Martin still prefers to keep the Others looming offscreen for now.
Benioff and Weiss, instead, have been trying to show they haven't forgotten about the White Walkers. Back in season two, they invented a scene in which Jon Snow sees a White Walker taking away Craster's son. Then, in season four, they invented a scene showing a Walker taking another of Craster's sons and changing its eyes to blue. This was all heavily implied to be going on in the books, but not directly shown.
That scene last year revealed another tantalizing tidbit — that the White Walkers appear to have a leader with a horned crown. And some HBO supplementary material revealed that leader's name — the Night's King, a name Benioff uses in this week's "Inside the Episode" video.
We also learn another way the White Walkers can be killed, in addition to dragonglass. Jon's Valyrian steel weapon kills his Walker opponent, rather than shattering on contact as other weapons have. This has been set up in the books, but we haven't seen it in action. (Early in the fourth book, A Feast for Crows, Sam reads in an old book that a mythical hero killed others with a blade of "dragonsteel," and he and Jon speculate that that could refer to Valyrian steel.)
Of course, some elements of the Walkers' attack appear to be show-only inventions. The fast-moving skeletons, for instance, don't appear in the books — the corpses the Others reanimate have flesh on them and are slow-moving. These skeleton troops, introduced in the season four finale, were the idea of director Alex Graves, so they're likely not an adaptation of Martin's future plans.