We are Geats and we have heard of your sorrow, I have fought many monsters and I am here to fight this one as well.
Grendel was caught off guard to see the hall guarded, but it didn't stop him from feasting on his first prey, when he grabbed onto a "sleeping" Beowulf. But Beowulf with all his strength grabbed onto him and the frightened Grendel couldn't get away.
Grendel's mom, came from the depths of the lake to avenge her son, killing Beowulf's friend along the way. Beowulf seeking justice waon his way to go after her.