summarize what happens during the battle between grendel and beowulf at herot

As Grendel plods through the darkness, heading toward Heorot for his nightly slaughter. He grips the hall door and rips it away. As he enters, his eyes fall upon the warriors sleeping. Little does he know that Beowulf is watching. Grendel reaches for and completely swallows one of the warriors. Next the monster reaches for Beowulf, who is ready for him. Beowulf seizes the vicious claw and holds on to it. Grendel is at first confused, then fearful as he tries to pull away. Still Beowulf hangs on tight. Grendel's wrenching and bellowing brings the Danes out of their slumber and nearly breaks Heorot. Grendel desperately wants to be free and go home, but Beowulf keeps him in place. All the warriors don't know how to help. Grendel is in such agony that he finally rips from Beowulf's grasp and runs away, leaving a bloody trail and his arm behind.