Orpheus was the son of Apollo and Calliope (one of the muses.) It was no wonder that Orpheus was a gifted musician, with such talented musical parents. Orpheus was more than gifted. His music was magical. When he played the lyre, as his father taught him, his songs could cast spells and soothe  savage beasts. 

Orpheus loved his wife, Eurydice. When she died, he traveled into the Underworld. He begged his great uncle Hades to allow his wife to come back to earth as herself, not reborn as someone else. 

Ever a soft touch, Hades agreed. There was one condition, though. Hades agreed to let Eurydice follow her husband back to earth and life. But, during the trip, Orpheus had to promise not to look back until both he and his wife were safely back on earth.  

But Orpheus was worried. He was afraid that perhaps his wife might need his help - it was a very scary trip back to the surface. He worried that perhaps Hades would not send her after all. To reassure himself that all was fine, he risked a quick look behind him, and lost his wife forever.