Hrothgar, King of Denmark, has built a "mead hall" (large tavern) where folks can eat, drink and entertain. However, the joy quickly fades when a large monster name "Grendel" crashes the festivities by wrecking the hall and killing many Danes.
A great Geatish warrior named "Beowulf" hears about the monster and the trouble it's causing. He and his men travel by ship from Sweden to the shore of Denmark to help them fight Grendel. Beowulf has the strength of thirty men and kills the giant.
The next morning, the local people learn of Grendel's defeat by Beowulf. Beowulf is rewarded with praise and treasure. But the next night, Grendel's hag of a mother comes and attacks the hall to avenge her son. Beowulf tracks her down and kills her.
After a few days of hero worship, Beowulf returns to Geatland and rules as king for fifty years. His fate comes after killing a large dragon and not surviving the fight.