She was killed by a snake, Orpheus decided to try to get her back, by going to the underworld
I'll make you a deal, you wife will follow you, but if you look back while going out she will disappear.
Give my wife back!
When he was almost out he didn't trust Hades, so he broke the deal and she disappeared. He saw her disappear in his eyes.
He played his music, even more majestic then before. But when people came to listen he pushed them all away, and then the Three Ladies Of Thades were tired of him then they killed him. After his death he joined his love in the underworld.