(This story has many different versions, so I’ll add the other parts along with it, which may make it a bit less fun to read, but will at least make it so that no one feels cheated out of part of the story along the way)
Usually in this story, Hades merely falls in love with Persephone. However, Ovid, going for drama, adds a marvelous little detail. According to that story, when some monster fell to earth, an earthquake occurred. Hades, always very careful of his domain, raced about to find what had gone wrong so that his gloomy kingdom would not be exposed too long to the upper world. Aphrodite, watching, came up with an idea. You see, Hades had long been impervious to her domain, which rather upset her, so she was quite determined to make him fall passionately in love with someone. Meanwhile, she had another problem. Demeter’s daughter, Persephone, had plans to become a maiden Goddess, and three were already far too many for Aphrodite. So, she commanded Eros to shoot one of his arrows into Hades to make him besotted with Persephone.
(for Ovid's actual version, found in his Metamorphasis Book V check out documents or From Ovid's Metamorphasis )
Though this part does not occur in most myths, Hades does become besotted of the beautiful Persephone. He talks with Zeus who gives him permission to carry the girl off, and also makes arrangements with Gaea to produce a beautiful flower. He says nothing (with good cause, if you think about it) to Demeter or Persephone.
Cut to Persephone playing with the daughters of Oceans on the fields of Sicily. She moves away from them after spying a beautiful asphodel (daffodil/narcissus or sometimes a black bush with ruby red berries instead) on the ground. As she plucks the flower (or as she pulls up the bush), the ground opens underneath her and Hades seizes her. Only Helios (the sun) sees her fall, and only Hecate hears her scream. In many cases a swineherd, Triptolemus, looses a few pigs down the gaping hole and also notices her absence.
Persephone is shortly made queen of the sunless world, and is decked in jewels, crowns, silk, all the finery that the Lord of Wealth can offer to her. She grieves for her flowers, the sun, and most of all her mother, though, and refuses to eat or drink anything. (I still think that the best touch is the time when Hades and Persephone end up playing jacks with dimonds and rubies on the floor of the palace of the underworld, and where they play hide-and-go seek with the helmet of invisibility. Now, wouldn't that be fun?)
Meanwhile Demeter went into a frenzy searching for her daughter. The earth goes barren, rain and snow falls, and winds howl. People begin to starve, and life becomes very unpleasant.
She turns into an old woman, until she is found by a group of princesses (the daughters of Celeos). She introduces herself as Doso, the Giver, who was carried from Crete by pirates. She is brought to their house as a nursemaid for their baby brother, Demophoon. She takes the baby and holds him over the fire each night, turning him into a God. However, a night before he would have become a God, the queen comes in and screams at what this woman is doing to her baby. Demeter changes into her Goddess self and the woman apologizes profusely. She orders the woman to build her a temple to repair for the sin, and departs.
She's also bothered by this little boy named Ascalaphus who bugs her asking why she's so sad, and being annoying. She changes him into a lizard. In some cases, she immediately feeds him to a hawk. In other stories, she rides off, and he follows her hoping that Demeter, who always liked children, will change him back before he is swallowed by a hawk.
The search for Persephone continues, as does the destruction of the earth. Finally, with the help of either Triptolemus or Hecate, she learns what has happened to Persephone. She then questions Helios, and with the information she needs, confronts Zeus.
Zeus admits to conspiring with Hades, but will not let Persephone return. Demeter continues her rage, until Zeus realizes that he’ll never get sacrifices anymore if she’s allowed to kill all the people. So, he releases Persephone, so long as she has eaten nothing, (it’s an ancient rule) and sends Hermes after her.
Hermes reaches the underworld, and tells Persephone to come. Hades is very civil (always a civil God, though trickiest at that time) and asks to have a moment alone with his wife. He asks his wife to be speak kindly of him, and remember him, as he is no unworthy husband, being brother to Zeus and ruling a third of the universe. He promises that she shall be revered and have control over all that die, and that she shall be praised with him forever. Persephone is persuaded to eat half a pomegranate, six seeds, or any other number convenient at the time, and then returns with Hermes.
In some other stories, she's in her garden with Ascalaphus when she ends up eating a pomegranate's seeds. She's then called out, and Ascalaphus tells Hades that Persephone has eaten the seeds.
As she returns Demeter embraces her, but asks if she has eaten anything. Persephone at first lies, saying "no", but eventually it becomes apparent that she has. (then it’s, I was forced to, or I was tricked, in many stories) Eventually she is forced to spend part of the year in the underworld (or all in a few stories where she falls in love with her dark husband and stays there of her own will) and part of the year on earth with her mother. When she is in the underworld, it is winter. Hecate is to follow Persephone about to make sure that the deal is kept. (Argh! When mother isn't watching over me, my husband is! And I'm always watched by a hag! Why me?) It is important to remember, for symbolism's sake, that Persephone ate the seeds of her own free will, and so in some sense consented to be Hades' wife. It is also important to remember that Hades, Zeus, and Gaia conspired on this, which makes Hades less of a villian than he later seems to become.