In his cave, Grendel's mother swears revenge over his corpse. She travels to Heorot and slaughters Beowulf's men while they are sleeping. Hrothgar tells both Beowulf and Wiglaf, who had been sleeping outside the hall during the attack, that it was the work of Grendel's mother. She is the last of the Water Demons, who were thought to have left the land. Hrothgar's adviser, Unferth, offers Beowulf his sword Hrunting to slay Grendel's mother. Beowulf and Wiglaf travel to the demon's cave to slay her. Beowulf enters the cave alone and encounters the demon, who takes the form of a beautiful woman. He tries to kill her with the sword but fails due to her magic; instead, she seduces him with promises to make him king in exchange for the drinking horn and a son to replace Grendel. Afterwards, Beowulf returns to Heorot with Grendel's head and announces he has killed his mother the demon. He recounts embellished stories of a fight, claiming he left the sword impaled in the body of Grendel's mother and lost the golden drinking horn in the battle. Hrothgar speaks to Beowulf privately, and asks if he truly killed Grendel's mother. Despite Beowulf's boasting and calling Grendel's mother a 'hag', Hrothgar is not fooled. He too had been seduced by the demon, and Grendel was the result of their tryst. Hrothgar claims all that matters is that Grendel is dead and the curse is no longer his to bear. Beowulf gasps, realizing that the curse had been passed unto him after his encounter with Grendel's mother. Hrothgar declares Beowulf to be king upon his death and he then commits suicide by jumping from the castle parapet onto the beach below. The water demon appears as a gold light in the surf, and drags Hrothgar's corpse into the sea as the crowd kneels to King Beowulf.