"Beowulf" is a poem that describes events that happen to Danish King Hrothgar and his great hall, Heorot. King Hrothgar and his people are plagued by Grendel, a monster who attacks Heorot every night to pillage and kill Hrothgar's men. Beowulf is a foreigner from Geatland who travels to aid King Hrothgar by protecting his people and his hall.
In the poem, Beowulf engages in combat with Grendel. Beowulf tears Grendel's arm off, and Grendel flees from Heorot into the wilderness where he dies. Grendel's mother finds out about the death of her son and seeks revenge. She goes to Heorot to avenge her son's death, but gets scared and goes into hiding in her lair. Beowulf and his army seek her out in her cave under the lake. Beowulf dives into the lake and slays Grendel's mother with a blade he took from Grendel's mother's treasure. He takes her head and the blade back to the surface.
Beowulf is honored as a hero. He returns to his home in Geatland where he eventually becomes King of the Geats. In the poem, Beowulf's final battle is with a dragon that attacks his people. He defeats the dragon but becomes mortally wounded in the process. The poem ends with Beowulf's burial and his people mourning the loss of their great king.