On learning of this loss on the morrow, Hrothgar is overcome with grief, and Beowulf, hearing his lamentations, suddenly appears to inquire what has occurred.  On learning the ghastly news, he volunteers to complete his work and avenge Aeschere by attacking Grendel’s mother in her own retreat.  But, knowing the perils he is facing, he makes his arrangements in case he should never return, before following the bloody traces left by the monsters.  Then he hastens to the pool, where he finds Aeschere’s head set aloft as a trophy!  Gazing down into the depths, Beowulf now perceives the waters are darkly tinged with the monster’s blood, but nevertheless plunges boldly into their depths, where he swims about a whole day seeking Grendel’s retreat.  Guided at last by a phosphorescent gleam, our hero finally reaches a cave, after slaying on the way a number of monsters sent to check his advance.  On nearing the giants’ den, a strong eddy suddenly sweeps him within reach of Grendel’s mother, who, clutching him fast, flings him on the floor, and is trying to find a joint in his armor, so as to kill him with her knife, when Beowulf, snatching a sword hanging from a rocky projection, deals her so fierce a blow that he severs her head from its trunk.

  Then he saw amid the war-gems a weapon of victory,
  An ancient giant-sword, of edges a-doughty,
  Glory of warriors:  of weapons ’twas choicest,
  Only ’twas larger than any man else was
  Able to bear in the battle-encounter,
  The good and splendid work of the giants. 
  He grasped then the sword-hilt, knight of Seyldings,
  Bold and battle-grim, brandished his ring-sword,
  Hopeless of living hotly he smote her,
  That the fiend-woman’s neck firmly it grappled,
  Broke through her bone-joints, the bill fully pierced her
  Fate-cursed body, she fell to the ground then: 
  The hand sword was bloody, the hero exulted. 
  The brand was brilliant, brightly it glimmered,
  Just as from heaven gem-like shineth
  The torch of the firmament.

The blood from this monster, pouring out of the cave, mingles with the waters without, which begin to seethe and bubble in so ominous a way that Hrothgar and his men, exclaiming Beowulf is dead, sadly depart.  The hero’s attendants, however, mindful of orders received, linger at the side of the mere, although they cherish small hope of ever beholding their master again.

Having disposed of Grendel’s mother, Beowulf rushes to the rear of the cave, where, finding Grendel dead, he cuts off his head, and with this trophy makes his way up through the tainted waters, which melt his sword, so that he has nothing but the hilt left on reaching the shore.

                   The sword-blade began then,
  The blood having touched it, contracting and shrivelling
  With battle-icicles; ’twas a wonderful marvel
  That it melted entirely, likest to ice when
  The Father unbindeth the bond of the frost and
  Unwindeth the wave-bands, He who wieldeth dominion
  Of times and of tides:  a truth-firm Creator.