On Unbelievable Stories (40)

The tragic myth told about Alcestis is that, when Admetos was about to die, Alcestis volunteered to die on his behalf, and that Heracles, on account of her piety, rescued her from Thanatos [‘Death’] and returned her to Admetos. I don't think anyone is capable of bringing someone back to life after they have died.

Rather, something like this happened. When Pelias' daughters killed him, Pelias’ son Acastos went after them, wanting to kill them to avenge his father. He captured the other sisters, but Alcestis escaped to Pherai to her cousin Admetos. There she sat as a suppliant at his hearth so that Admetos couldn't agree to Acastos' demands to give her up. Acastos positioned a large army around the city and began to attack them with fiery missiles. During the night, Admetos went out but happened upon the enemy captains, and he was captured alive. Acastos threatened to kill him unless he gave up Alcestis even though she was a suppliant. When Alcestis learnt that Admetos was about to die because of her, she came out and handed herself over. Acastos released Admetos and apprehended Alcestis. And so people would say, Alcestis is so brave she was willing to die for Admetos. This certainly did not happen as the myth says it does.

It was then that Heracles was passing through from somewhere with the horses of Diomedes. When he arrived Admetos welcomed him as a guest. Admetos lamented the misfortune of Alcestis and Heracles became indignant. [*] He attacked Acastos and annihilated his army. He then divided up the spoils among his army and handed Alcestis over to Admetos. And so people would say that Heracles had come along and rescued Alcestis from death. The myth was fabricated from these actual events.