A monster, Grendel, has been attacking the Denmark locals for 12 years. Grendel has been eating the King's (Beowulf) soldiers.
Beowulf discusses with the kingdom locals, that he will declare a fight with Grendel for peace in the kingdom. The kingdom locals are very keen on the idea.
I declare a fight!
Beowulf fights Grendel for peace in his kingdom. Beowulf kills Grendel by chopping off his arm. Grendel's arm floats in the sea.
I killed Grendel!
Beowulf fights Grendel's Mother after she takes revenge over her son's death. Beowulf kills Grendel's Mother and the kingdom is at peace.
Beowulf was given lots of gifts to symbolise the kingdom's appreciation for killing Grendel and his wicked mother.
50 years later... Beowulf is getting very old and after years of peace, they are disturbed. A dragon attacks the kingdom and fights a deadly battle. In the end, Beowulf kills the dragon but gets killed too.