Demeter was the mother of a girl named Persephone. They had a very close relationship. They both were goddesses that helped grow crops.
When persephone goes out to the meadows to get flowers for her mother, she smells a wonderful scent that her mother would love, she goes to find it, but she doesn't know the greek god hades is spying on her and wants her to be his wife, out from the underworld, Hades creates a crack in the earth and takes Persephone down and this is when she went missing unseen and her mom was heartbroken.
When Persephone got caught by Hades, she wouldn't do anything until Hades proposed to her and they made an agreement to let Persephone leave for 6 months to see her mother each year and then she'd go back to Hades.