Orpheus and Eurydice were about to be married, but she was bitten by a snake while picking flowers and died.
Orpheus was devastated and went to the Underworld to see if Hades would allow him to have Eurydice back. He was able to get through the monsters because his music was so beautiful.
Hades makes a deal with Orpheus. If he can walk out of the Underworld without turning around, Eurydice will follow him and be allowed to return to earth. However, if he turns around before he leaves the cave, she will remain with Hades.
Orpheus begins walking out of the Underworld, but he's not sure if he should trust Hades. So he turns around and Eurydice vanishes and now has to stay with Hades.
The women of Thrace were maddened by Dionisys and killed Orpheus because he wouldn't play music.