Grendel, the ferocious demon who was irritated by the presence of the Heorot Hall which was a throne room but also used for recreation, dominated it for more than 12 years. Even King Hrothgar could not deal with the formidable monster. The story spread and Beowulf heard about it.
Beowulf, a follower of King Hygelac, the son of Ecgtheow and more importantly, the mightiest warrior on the planet, decided to travel to Denmark from Geatland and defeat Grendel. He travelled with the accompany of 14 other warriors by a boat.
Beowulf and the Geats pretended to sleep and waited for Grendel's inevitable assault. When Grendel came, Beowulf fought him without any armor or weapon. Eventually Beowulf mortally wounded Grendel by tearing one of his arms away.
King Hrothgar and his queen returned to Heorot Hall to celebrate after Beowulf has defeated Grendel. Hrothgar spoked there, acclaiming Beowulf as his adopted son. Subsequently, he awarded Beowulf with gifts.
Grendel's mother, grieving for the lost of his son, decided to take revenge. She came to Heorot Hall at night and killed several people. Grieving, King Hrothgar asked Beowulf to kill her. Beowulf found where she was easily because she was carrying a corpse. Beowulf jumped into the lake, killed her as well as decapitated Grendel and brought his enormous head back.
The sleeping dragon was waken up by someone who steals a goblet from its hoard of treasure. The dragon attacked the Geat people every night. As the King, Beowulf stood up, but this time, he carefully built armors as well as weapons and brought 12 other warriors with him. He made the last boast before the fight. In the end, he slew the dragon, but he died from the poisoned wound as well. Before he dies, he thanked god for the treasure he got from the dragon and inherited his golden collar to Wiglaf.