Althaea was the daughter of Thestius and Eurythemis in Apollodorus's genealogy, a princess of Aetolia in western Greece. She married Oeneus, king of Calydon, the ruler associated with Dionysus's gift of the vine. Their children included Meleager, the prince who would lead the famous boar hunt; Deianira, who would later marry Heracles; and Gorge, who married Andraemon. Other children and variations in their parentage appear in ancient accounts. The household began as a place of royal promise, but the stories attached to it repeatedly turn marriage, divine favour and family loyalty into sources of danger.

The doom began soon after Meleager's birth. In Apollodorus's version the three Moirai, or Fates, appeared when the child was seven days old and declared that he would die when the brand burning on the hearth was consumed. Althaea acted at once. She snatched the wood from the flames, extinguished it and kept it hidden in a chest. As her son grew, the object remained under her protection. The bond between the child's life and the wood remained: the mother who had saved him also held the means by which he could die.

Meleager grew into a celebrated hero and was counted among the Argonauts. The catastrophe at Calydon began when Oeneus omitted Artemis from the offerings of his harvest sacrifice. The goddess of the hunt answered the neglect by sending a gigantic boar to ravage his land. The creature destroyed crops and threatened the people, and Oeneus summoned hunters from across Greece. Ovid gives the monster a terrifying poetic presence, with blazing eyes, great tusks and a body that seems too large for an ordinary animal. These details belong to the myth's imagery of divine punishment, not to the description of a historical beast.

Meleager led the expedition. Among the hunters were Jason, Theseus, the Dioscuri, Peleus and Atalanta, whose participation became central to the dispute that followed. The accounts differ in their detailed sequence of wounds. Apollodorus says that Atalanta first struck the boar in the back, Amphiaraus hit its eye and Meleager killed it with a blow to the flank. Ovid gives his own extended account of the hunt. Both traditions make Atalanta's successful shot important to Meleager's decision about the prize. The hunt brought the heroes together, but the division of the spoils would turn victory into a family disaster.

Meleager awarded the hide to Atalanta, both in recognition of her success and because he loved her. Althaea's brothers objected to a woman receiving the prize. In Ovid they are Plexippus and Toxeus, who claimed the spoils by their own standing and kinship if Meleager would not take them. They seized or disputed what he had given her, and the quarrel became violent. Meleager killed them both. The dead men were not merely rivals from another house: they were his mother's brothers. His triumph over the boar had created a new demand for vengeance within the family it was meant to protect.

Althaea was giving thanks for her son's victory when she saw her brothers' bodies being brought home. Celebration turned to mourning, and then to anger against their killer. She retrieved the hidden brand and prepared a fire. Ovid dwells on the struggle that followed: four times she moved to cast the wood into the flames, and four times she held back. As a mother she wanted Meleager to live; as a sister she demanded payment for the dead. She called on the avenging powers to witness her act and argued with herself over the claims of birth, blood and justice. Finally she turned her face away and threw the brand into the fire.

Far away, Meleager felt his life being consumed by a fire he could not see. Ovid describes a death without the visible wound of battle, while the hidden wood crumbled and Althaea's vengeance became irreversible. He called on his family, including his wife Cleopatra and, at the end, his mother. The palace filled with mourning. Althaea did not survive the consequences of her choice: she took her own life. The accounts differ in the manner of her death, with Ovid describing a blade and Apollodorus giving hanging. The common thread is that the revenge which destroys her son also destroys the woman who once rescued him.

The tragedy extended to Meleager's sisters. Traditions of the Meleagrids tell how their unending mourning led to their transformation into birds, with Gorge and Deianira excepted; Antoninus Liberalis connects the birds with Leros. Homer's earlier narrative in Iliad 9 must be kept distinct from the fatal-brand story. There Althaea curses Meleager after he kills her brother during the conflict with the Curetes. Meleager withdraws from the fighting, then returns when Cleopatra appeals to him. Homer does not narrate his death in that passage. The different tellings share the pressure of kinship and anger, but they do not provide one interchangeable account of how his life ended.