Beowulf begins with a history of the Danish kings, starting with Shild and leading up to the reign of king Hrothgar, Shilds great-grandson. Hrothgar is well loved by his people and is successful in war. He builds a lavish hall ,called Herot, to house his vast army, and when the hall is finished the Danish soldiers gather under its roof to celebrate.
Grendel, a monster in human shape who lives at the bottom of a nearby swamp, is provoked by the singing and horsing around of Hrothgars followers. He appears at the hall late one night and kills thirty of the warriors in their sleep. For the next twelve years the fear of Grendels potential fury casts a shadow over the lives of the Danes. Hrothgar and his advisers can think of nothing to appease the monsters anger.
Beowulf ,the prince of the Geats, hears about Hrothgars troubles, he gets fourteen of his bravest Geats, and sets sail from his home in Sweden. The Geats are greeted by the members of Hrothgars court, and Beowulf boasts to the king of his previous successes as a warrior, particularly his successes in fighting sea monsters. Hrothgar welcomes the arrival of the Geats, hoping that Beowulf will live up to his reputation. During the banquet that follows Beowulfs arrival, Unferth, a Danish soldier, voices doubt about Beowulfs past accomplishments, and Beowulf, in turn, accuses Unferth of killing his brothers. Before retiring for the night, Hrothgar promises Beowulf great treasures if he meets with success against the monster.
Grendel appears on the night of the Geats arrival at Herot. Beowulf, true to his word, wrestles the monster barehanded. He tears off the monsters arm at the shoulder, but Grendel escapes, only to die soon afterward at the bottom of his snake-infested swamp. The Danish warriors, who had fled the hall in fear, return singing songs in praise of Beowulfs triumph. Hrothgar keeps his word and rewards Beowulf with the treasures he had promised. After another banquet all of the soldiers go to sleep.
Not knowing the warriors, Grendel had a mother and she was plotting to take revenge for her son. She arrives at the hall when everybody is sleeping and carries off Esher, Hrothgars chief advisor. Beowulf, rising to the occasion, offers to dive to the bottom of the lake, find the monsters home, and destroy her. he and his men follow the monsters tracks to the cliff overlooking the lake where Grendels mother lives. They see Eshers bloody head floating on the surface of the lake. While preparing for battle, Beowulf ask Hrothgar to protect his warriors , and to send his treasures to his uncle, king Higlac, if he doesnt return alive.
During the ensuing battle Grendels mother carries Beowulf to her underwater home. After a terrible fight Beowulf kills the monster with a magical sword that he finds on the wall of her home. He also finds Grendels dead body, cuts off the head, and returns to land, where the Geat and Danish warriors are waiting for him. Beowulf has now cleaned Denmark of the race of evil monsters.
The warriors return to Hrothgars court, where the Danish king delivers a sermon to Beowulf on the dangers of pride and on the fleeting nature of fame and power. The Danes and Geats prepare a feast in celebration of the death of the monsters. In the morning the Geats hurry to their boat, anxious to begin the trip home. Beowulf says farewell to Hrothgar and tells the old king that if the Danes ever need help he will gladly come to their assistance. Hrothgar presents Beowulf with more treasures and they embrace, emotionally, like father and son.
The Geats sail home. After recounting the story of his battles with Grendel and Grendels mother, Beowulf tell king Higlac about the feud between Denmark and their enemies, The Hathoboards. He describes the proposed peace settlement, in which Hrothgar will give his daughter Freaw to Ingeld, king of the Hathoboards, but he predicts that the peace settlement wont last long. Higlac rewards Beowulf for his bravery with territory, swords, and houses.
The meeting between Higlac and Beowulf marks the end of the first part of the poem. In the next part is dead, and Beowulf has been king of the Geats for fifty years. A thief steals a jeweled cup from a sleeping dragon who avenges his loss by flying through the night burning down houses, including Beowulfs own hall and throne. Beowulf goes to the cave where the dragon lives, vowing to destroy it single-handed. Hes an old man now, however, and his strength is not as great as it was when he fought against Grendel. During the battle Beowulf breaks his sword against the dragons side; the dragon, enraged, engulfs Beowulf in flames and wounds him in the neck. All of Beowulfs followers flee except Wiglaf, who rushes through the flames to assist the aging warrior. Wiglaf stabs the dragon with his sword, and Beowulf, in a final act of courage, cut the dragon in half with his knife.
Yet the damage is done. Beowulf realizes that hes dying, that he has fought his last battle. He asks Wiglaf to bring him the dragons storehouse of treasures; seeing the jewels and gold will make him feel that the effort has been worthwhile. He instructs Wiglaf to build a tomb to be known as Beowulfs Tower on the edge of the sea. After Beowulf dies, Wiglaf admonishes the troops who deserted their leader when he was fighting against the dragon. He tells them that they have been untrue to the standards of bravery, courage, and loyalty that Beowulf has taught.
Wiglaf sends a messenger to a nearby encampment of Geat soldiers with instructions to report the outcome of the battle. The messenger predicts that the enemies of the Geats will feel free to attack that know that their king is dead. Wiglaf supervises the building of the funeral pyre. In keeping with Beowulfs instructions, the dragons treasures is buried alongside Beowulfs ashes in the tomb. The poem ends as it began with the funeral of a great warrior. The major theme of this poem was the battle between good and evil.