Hwaet! Many tales have been told of the exploits of the brave, six-packed hero Gee (You wish – Ed.) as he journeyed through wind and storm over the whale road to the coin-operated magic lantern in Cromer to see the Beowulf movie, directed by Robert Zemeckis, and was entirely blown away. No, not by the wonderment of the smithes orthancum, which was great (though everyone else seems to be hung up on that) but by the adaptation. If Neil Gaiman and Roger Avary don’t get an Oscar nomination for best adapted screenplay then there’ll have been no justice.

The week before, I’d re-read the poem itself – a bilingual version, with the Old English text on one side and the Modern English on the other. The latter was by Seamus Heaney. Now, I am no more expert in King Alfred’s Englisc than is anyone else on the 06:05 from Norwich, but I knew enough to tell that Heaney’s translation, while rumbustious, plays somewhat fast and loose with the original. It was with justification that Tolkien scholar Tom Shippey referred to the Irish poet, in my hearing, as ‘Shameless’ Heaney.

The story, though, is clear enough. As every schoolboy knows, Good King Hrothgar of Denmark has built a fine mead hall, but festivities are continually interrupted by the monstrous Grendel. Enter Beowulf, warrior-prince of the Geats, who kills Grendel by ripping off his arm. The monster slinks back to his mother’s cave and dies. The mother, a water-demon, is even more ferocious than her son, and seeks revenge, but Beowulf dispatches her too – in single combat, deep in her watery lair. Heroic Beowulf returns to his own land where he rules wisely for fifty years, until he faces a dragon single-handed and dies in the attempt. So much is clear.

What the film does is very clever: it assumes that the poem that has come down to us is a bowdlerized propaganda version (which it assuredly is, having been through several scribal hands since its original composition) – and proceeds to tell us what really happened. In so doing the script exploits all sorts of odd foibles in the text, showing that Gaiman and Avary well those passions read, stamped on those lifeless things.

First, to show us that the scriptwriters knew their hauberks from their byrnies, the film establishes its integrity by following the story almost line for line (allowing for the usual compressions of adaptation) right up until the point at which Beowulf has to go looking for Grendel’s mother. This is shown by the film’s inclusion of an extended by-play in the poem, in which Beowulf is upbraided by Hrothgar’s advisor Unferth for being not quite the hero he claims to be, having lost an epic oceanic swimming race with another hero, Breca. Beowulf responds by saying that he only lost because he had to slay several sea-monsters along the way. This is the sort of episode which any conventional script would have cut – but the film has it, note for note.

It’s when Beowulf enters the subterranean world of Grendel’s mother that the plot of poem and script diverge. Rather than being a monster of conventional stripe, Grendel’s mother is a slinky seductress: Angelina Jolie, even more pneumatic than usual, if such is possible, with a long plait of hair that slinks around like a serpent of its own volition. She proves indestructible, and Beowulf can only escape by making a faustian pact in which she will grant him, in effect, eternal life.

When I saw the trailer I was inclined to dismiss this as bunk. But a closer reading of the poem revealed two crucial things. The first is that there is no clear physical description of Grendel’s mother in the text, a fact which allows any scriptwriter considerable licence. The second is that only Beowulf was witness to her slaying. He returns to the upper world with the head of Grendel, not that of his mother. The world hails Beowulf a hero, both in poem and film. Only in the film is Beowulf forced to live with his guilty secret.

But if pumped-up Angelina doesn’t look like a ferocious monster, what does she look like? Even here, the writers cleave close to ancient sources. Grendel’s mother is a lamia, a creature with the face or torso of a woman, the tail of a snake, a creature who exists to ensnare hapless men. A lamia is irresistably gorgeous, as Keats notes in his poem of the same name:

She was a gordian shape of dazzling hue,
Vermilion-spotted, golden, green, and blue;
Striped like a zebra, freckled like a pard,
Eyed like a peacock, and all crimson barr’d;
And full of silver moons, that, as she breathed,
Dissolv’d, or brighter shone, or interwreathed
Their lustres with the gloomier tapestries—
So rainbow-sided, touch’d with miseries,
She seem’d, at once, some penanced lady elf,
Some demon’s mistress, or the demon’s self.
Upon her crest she wore a wannish fire
Sprinkled with stars, like Ariadne’s tiar:
Her head was serpent, but ah, bitter-sweet!
She had a woman’s mouth with all its pearls complete:
And for her eyes: what could such eyes do there
But weep, and weep, that they were born so fair?
As Proserpine still weeps for her Sicilian air.
Her throat was serpent, but the words she spake
Came, as through bubbling honey, for Love’s sake,
And thus; while Hermes on his pinions lay,
Like a stoop’d falcon ere he takes his prey.

But fair Angelina has an older model in literature, and a closer, as I discovered in a secondhand bookshop just this Saturday. When I read it, it made my hair stand on end.

But full of fire and greedy hardiment
The youthfull knight could not for ought be staide,
but forth vnto the darksome hole he went,
And looked in: his glistring armor made
A litle glooming light, much like a shade,
By which he saw the vgly monster plaine,
Halfe like a serpent horribly displaide,
But th’other halfe did womans shape retaine,
Most lothsom, filthie, foule, and full of vile disdaine.
And as she lay vpon the durtie ground,
Her huge long taile her den all ouerspred,
Yet was in knots and many boughtes vpwound,
Pointed with mortall sting…

Not only a sharp description of the movie version of Grendel’s mother, but a portrait of the hapless hero’s encounter with her. What’s more, this graphic description (in Edmund Spenser’s Faerie Queene, Book I, Canto I, 14-15, if you want to know) is meant to be allegorical: the monster stands for Sin or ‘Errour’, and occupies the same place in Spenser’s moral universe as Angelina’s character does in that of the cinematic Beowulf.

The world hails Beowulf as a hero – and that’s the version that comes down to us. The movie script proceeds therefore with Beowulf lauded as hero and king, living a life and a lie. It turns out that Hrothgar bore the same guilty secret, which he vouchsafed only to his wife, Queen Wealhow, whom Beowulf inherits after Hrothgar’s (cinematic) death, and it is associated with a golden talisman (cursed, as these things inevitably are in Norse legend). Beowulf is a hero, then, but under false pretences – he knows he cannot be slain, and so the risks of battle, and the attendant acts of courage, are denied him. This is why, late in life, he feels he must slay the dragon and die in the attempt – which he can only do because the dragon turns out to be one of Angelina’s avatars. Only … well, I’ll be giving away the killer punch.

The script is so intelligent that it not only plays with the text at a respectfully intellectual level: it also nods to the religious ambiguities thrown up by its darksome editorial history. When Beowulf was composed in the mists of the dark ages, the ethics of the societies it described were based on what Tolkien called a ‘theory of courage’ – that it was right for men to die in battle, even when they knew their cause was lost. Notably, in the Last Battle of Norse mythology, between the Gods and the Monsters, it is the Gods that lose. This ethic is profoundly antithetical to the Christian message of hope and salvation.

However, the only known copy of Beowulf that has survived was made in the 13th century, when England had been Christian for half a millennium, and the poem is overlain with many Biblical references. The film plays up to this aspect nicely. When Hrothgar, Beowulf and Unferth are wondering which Gods to propitiate, Unferth wonders whether they should offer prayers to Christ, the ‘New Roman God’. The response is characteristically Norse – that the Gods will not help men who do not take responsibility for their own actions. But as the film closes, Unferth has become a priest, and brings warning of the ravages of the dragon.

True, the superstructure of the film – its technical excellence – is a fine thing, but one should not be distracted by this from the story and the excellence with which Gaiman and Avary have adapted it. As Tolkien wrote in his groundbreaking 1936 essay Beowulf: The Monsters And The Critics, scholars had spent too long admiring the poem as an archaeological or linguistic relic rather than as a rattling good yarn. What we should be looking at, said Tolkien, was the monsters. Advice that Gaiman, Avary and Zemeckis have taken great pains to follow.