Grendel's mother, unknown to the Danes or Geats, is plotting to avenge the death of her son. After the celebrations are over in Heorot and everybody is asleep, Grendel's mother appears out of her dwelling place, the swamp.
She enters the hall where the warriors are sleeping. They wake in time to ward off the attack with their swords but the monster manages to escape with one victim in her claws (this is Aeschere).
After she escapes, the warriors realize that she has managed to steal back Grendel's claw from where it has been hanging. The victim is one of Hrothgar's closest advisors, "the man he loved most of all men on earth." The king summons Beowulf and his men. There's a feeling of desperation in the air. We know Beowulf realizes that something is dreadfully wrong -- no doubt he can hear the uproar from the main hall- but he also knows that it's his job to convey confidence and self-control. At this moment, the young warrior seems wiser and more mature than the aging king.
Beowulf is told by the King that Grendel's mother has "avenged the feud" (Abrams, 44). The king, once again, asks Beowulf to help him. Beowulf, upon seeing the king's condition, says:
Sorrow not, wise warrior. It is better for a man to avenge his friend than much mourn. Each of us must await his end of the world's life. Let him who may get glory before death: that is best for the warrior after he has gone from life. Arise, guardian of the kingdom, let us go at once to look on the track of Grendel's kin.
On their way to the swamp, they discover Aeschere's bloody head sitting on top of the cliff. Grendel's mother has probably done this as retaliation for the Danes' hanging her son's claw up as a trophy. The "flood boiled with blood"(Abrams, 44).
Beowulf is now getting dressed for battle. As he is putting his armor on, Unferth offers his sword, Hrunting to Beowulf. After instructing Hrothgar to direct his treasures to Hygelac if anything should happen to him, the bold hero dives into the water.