The older a story is, the harder it is to scrub it back to its core. Generations of undergraduates have had "Beowulf" as a set text for translation and know it not just as a story but as a way of studying the Anglo-Saxon love of obscure riddling phrases as epic formulas, of discussing how the story read when it was all pagan, all the time, before Christian monks wrote it down, of comparing it with the epic traditions of the Mediterranean—much of the time, in other words, discussing almost everything about it except the story. Tolkien tried to provide a corrective to this with his essay "The Monsters and the Critics," but was only moderately successful—we still have to remember that there is a basic truth which is that Beowulf is a story of a hero who kills two monsters, and then gets old, and fights a dragon and dies.

Robert Zemeckis's film of Neil Gaiman and Roger Avary's script is not so much a film of the much-studied text as it is of that fundamental story rethought and reimagined. It is possible, always, to say of such retellings, why bother? Why fix what is not broken? And yet much that is most interesting in the arts has always been an appropriation of what already existed for the artists' own purposes. In one sense, there can be no spoilers for such retellings, and yet, if they work, they make everything dangerously new.

One of the reasons why Zemeckis decided that he wanted to film a script that Gaiman and Avary had written years earlier was his admiration for their work—he had worked with Gaiman on at least one project which did not come to fruition. Another was that he believed, with some justice, that the techniques of 3-D stop-motion animation with which he had experimented in The Polar Express (2004) cried out for the fantastic epic material to which they could do justice. For the director, then, this is in part a film not just about story, but about the techniques through which story is told; given that epic as we know it is always a bastardized form in which mechanisms derived from oral culture are transferred across into literary culture, this is fair enough.

And yet, the take on the story adopted by Gaiman and Avary is deliberately subversive of the epic—it is a story about a man who is only too aware that he will be the subject of stories and makes a fatal compromise with that fact and its implications. It is a meditation on fame and its temptations, on what it is to have a persona in the eyes of other people that is more and other than the person you actually are. At one point in the early scenes, the cynical warrior Unferth mocks Beowulf for losing a swimming race and for his excuse that he had to pause to fight sea monsters. We see his memory of fighting those monsters—one of them a highly sexualized though menacing merwoman—and hear him acknowledge laconically that he fought them—he tells us the story, but not Unferth. And his companion Wiglaf undercuts what we have just seen by saying that Beowulf has inflated the numbers—every hero has his critics. Both Gaiman and Avary are writers who have become the subject of cultish discussion—there are reasons why they were drawn to treating this subject in this way.

The first act of the film is largely parallel with the poem—King Hrothgar's new feasting hall is attacked by the monster Grendel, whom the noise of happy feasting has driven mad with pain. There are hints here of complexities absent in the original—both Hrothgar (Anthony Hopkins) and his young queen Wealthow (Robin Wright Penn) know things about the monster that they are not saying—but Beowulf arrives across the sea in answer to Hrothgar's requests for help and confronts the beast, tricks it and mortally wounds it using intelligence and leverage where simple brute force could never be enough. Those people who come to this film wanting mythic combat combined with the most extreme of violence will get it here—at one point Grendel chews off the head of a warrior who gets too close and it is one of the most gloriously disgusting things we have ever seen.

Grendel is indeed one of the points at which Zemeckis takes real risks and succeeds with them—he is a monster hard to see and take in, because so utterly unformed. His constant pain comes from the fact that he is a mongrel creature both monster and man and his parts do not fit together, his tongue utters language but in ways we cannot ever quite hear. Crispin Glover's movements, as captured by motion-capture, are a grotesque capering stumbling dance of death.

Beowulf is visited in his dreams by what seems to be a seductive Wealthow until she opens the mermaid's sharp-toothed maw at him and he awakes to find all his surviving men save Wiglaf butchered and hung like sides of meat. He heads into the hills to confront Grendel's avenging mother, and this is where Gaiman and Avary veer off from the original in the most startling of manners. We have seen the dying Grendel cradled by its mother, vast monstrous clawed hands that emerge from the deep lake, and a tentacle of immense reach and strength, but the version of the beast's mother that confronts Beowulf now is something entirely other.

We have gathered that Hrothgar knows more of the mother than he is telling and not been quite clear on how; what we meet now is a tall elegant naked woman whose clawed feet are almost stiletto heels and whose tentacle has become a sinuous braid. She is an object of sexual desire next to whom Wealthow looks like a provincial dumpling—a point underlined by the fact that Zemeckis not only casts Angelina Jolie but has her screen avatar resemble her far more closely than do any of the others. She is not just a figure of the seductiveness of evil, though, or just a misogynist's object of sexual unease—she is fame, the bitch goddess herself.

The film uses actors for their associative qualities as much as for their (quite considerable) skills—of course Hollywood always does this, and animated films notably do it a lot, but it is both peculiarly appropriate in a film which deals with fame and reputation and handled with conceptual wit. As Hrothgar, the drunken patriarchal king, Hopkins brings with him a whiff of sulphur and the unnatural which hints from the beginning at what we later find out; Ray Winstone was not the most obvious casting as Beowulf, but brings with him the flawed machismo of his underworld roles. John Malkovich is appropriately whiny and sinister as Unferth; Wright Penn was the idealized object of desire in Zemeckis's Forest Gump. We know who these people are and what their being here tells us—and that in turn tells us something about the nature of being a living legend in a time of heroes.

And in the film's third act, Beowulf reclaims his heroism as Hrothgar failed to do; the drinking horn he left as pledge with the demon who tempted him is returned and the kingdom he has inherited falls under threat from a dragon who is sometimes a vast golden man, as sinewy and idealized as its mother. The old hero does what heroes do—saving both his disillusioned wife and the young woman he has taken as his bedmate whose lives the dragon quite specifically threatens when it taunts him. As with Grendel, he does what is needful with no regard to consequences, disjointing his arm when he needs a crucial few inches of reach to pierce the creature's heart—and he dies alongside it, because that, rather than making deals with demonesses, is what heroes do. Wiglaf finds the horn in the surf as Beowulf's body burns out at sea: and he and Grendel's mother stare at each other fixedly in a wonderful final moment of openness and ambiguity.

The only thing that is not admirable about this film is the one thing that is the reason for its existence, which is the animation. To be precise, it is the fact that while everything from spearpoints to pebbles to waves is realized with wonderful precision, and monsters are as fluid and sensuous in their movement as demons have ever been in film, the design of the actual people is so close to being perfection that its falling short is more noticeable than if it were not so close. All of the characters look almost real, and yet have that pudding dough quality we associate with fantasy artists like the Hildebrandts. Seen in 3-D—as it really should be—this film takes the breath away, at least until the moments of repose, when something about the proportion of eyes to the rest of the face brings oneself back to oneself and disbelief along with it. Beowulf is a wonderful meditation on myth that shows us something important about the future of cinema while reminding us that we are still, alas!, in an imperfect present.

Roz Kaveney is a writer and reviewer living in London. Her books include Reading the Vampire Slayer, From Alien to The Matrix, and Teen Dreams; Superheroes! is forthcoming.