The film is a cooperative effort between Eurasia Motion Pictures (Canada), Spice Factory (UK), and Bjolfskvida (Iceland), and it was filmed in Iceland. The story takes place in the early half of the sixth century AD in what is now Denmark, but the filming of the movie in Iceland provided many panoramic views of that country's landscape. In 2006, a documentary of the making of Beowulf and Grendel, called Wrath of Gods, was released and went on to win six film awards in Europe and the U.S.
In 500 A.D., Hrothgar, king of Denmark, and a group of warriors chase a large and burly man, whom they consider a troll, and his young son, to the edge of deep cliff. The father directs his young son, Grendel, to hide from the attackers' view; whereupon The Danes shoot the father dead, and his dead body plunges onto the beach far below. The Danish king sees the young Grendel, but spares him. Later, Grendel finds his father's body and cuts the head off to take it home. Many years later, the severed (and mummified) head is inside a cave where the boy Grendel has become as large and powerful as his father, and plans revenge.
When Hrothgar finds twenty of his warriors killed inside his great hall, the Danish king falls into a depression. Beowulf, with the permission of Hygelac, king of Geatland, sails to Denmark with thirteen Geats to slay Grendel for Hrothgar. The arrival of Beowulf and his warriors is welcomed by Hrothgar, but the king's village has fallen into a deep despair and many of the pagan villagers convert to Christianity at the urging of an Irish monk. While Grendel does raid Hrothgar's village during the night, he flees rather than fight. Selma the witch tells Beowulf that Grendel will not fight him because Beowulf has committed no wrong against him.
A villager, recently baptized and thus now unafraid of death, leads Beowulf and his men to the cliff above Grendel's cave. When the villager is found dead, Beowulf and his men return with a rope and gain entry to Grendel's secret cave, where Beowulf's men mutilates the mummified head of Grendel's father. That night, Grendel invades Hrothgar's great hall, kills the Geat who desecrated his father's head, and leaps from the second story, but is caught in a trap by Beowulf. Grendel, refusing capture, escapes by severing his captive arm, and dies near the site of his father's death, where his body is claimed by a mysterious webbed hand. Thereafter Hrothgar admits to Beowulf that he had killed Grendel's father for stealing a fish but had spared the child Grendel out of pity. Grendel's severed arm is kept by the Danes as a trophy. In revealing more about Grendel, Selma recounts that Grendel had once clumsily raped her and has protected her since that day; and Beowulf becomes her paramour.
The Danes are later attacked by Grendel's mother, the Sea Hag; and Beowulf slays her with a sword from among her treasure, and then notices that the battle was being observed by child of Grendel and Selma. Later Beowulf, with Grendel's son watching, buries Grendel with ceremony. Shortly thereafter, Beowulf and his band of Geats leave Denmark by ship, having warned Selma that she must hide her son, lest the Danes destroy him.
The film attempts to retell the classic tale as a historical epic. Andrew Rai Berzins, in his blog, states that he intended that Grendel resemble a sasquatch. Other viewers feel that Grendel and his father are remnants of Neanderthals survived in isolated populations in the far north. Beowulf as presented constantly doubts the Danes' assertion (and later, that of his own men) that the troll is purely evil. Accordingly, Beowulf deeply regrets the need to destroy Grendel.
Another theme of the film is that of Christianity's introduction into pagan civilization. As Grendel's reign of terror continues with no end in sight, the people of the village turn away from their Norse gods, which seem to offer no help, to the Christian Jesus, who they are told forgives all.
The film received generally mixed and average reviews from professional critics; it scored 53% at Metacritic and 48% at Rotten Tomatoes. Most critics praised the film's cinematography, its brutal action sequences, and aspects of its revisionist script, but criticised the dialogue and some of the acting.
William Arnold of the Seattle Post-Intelligencer writes, "The film's near-fatal flaw is its dialogue, which had to be invented wholesale from the Old English text. It alternates between sounding stagy and anachronistically hip – with more overuse of the F-word than any two Samuel L. Jackson movies. It's a big mistake." Nevertheless, Arnold eventually recommends the film for "keeping its strain of rowdiness and violence in control, and lending the tale the kind of somber respect filmmakers tend to give adaptations of Shakespeare and Dickens."
Lisa Schwarzbaum of Entertainment Weekly commends director Gunnarsson for his "[focus] on the more interesting psychology of tribalism." Bill Gallo of Village Voice writes, "It's good, bloody fun that stirs the intellect whenever it feels like it, and as a swashbuckler, the dead-game Butler outswings just about anyone in Troy or Kingdom of Heaven or Tristan & Isolde."
Mick LaSalle of the San Francisco Chronicle says, "Imagine the worst Deadwood episode ever, and you'll get an idea of the general tone of Beowulf & Grendel, which is full of anachronistic cursing, tortured syntax, dark humor and lots of hairy, homely, filthy-looking people. The filmmakers get their point across in about 30 minutes, leaving 70 more for severed heads and period charm. There's no charm."
Todd McCarthy of Variety (magazine) agrees, writing, "Director Sturla Gunnarsson seems aware of the savagery intrinsic to the story, but is unable to mine it deeply, proving too genteel in the end to make a genuinely creepy or disturbing film." Liam Lacey of The Globe and Mail concludes, "The movie is a lumbering and ludicrous mess."