Tell what happens to Grendel after he flees heorot.

Grendel went to the battle with the other people you already got it

Their battle concludes with Beowulf's ripping Grendel's arm off, fulfilling his promise to Hrothgar to kill the monster with his bare hands. Beowulf nails Grendel's severed arm to the mead hall rafters and, although Grendel runs away, he is later found to have bled to death in his underwater lair.