Answer:
It isn't really Demeter who saves Persephone, but Zeus.

After Persephone is abducted by Hades, Demeter (the goddess of the harvest, and mother of Persephone), begins to neglect her duties. Humans begin to go hungry, so Zeus sends Hermes to the underworld, to talk to Hades. (Hades gives Persephone back, but she has eaten in the underworld and must return for a period each year. This myth explains the winter.)
First answer by Despairinthestands. Last edit by Despairinthestands. Contributor trust: 1 [recommend contributor recommended]. Question popularity: 0 [recommend question].