It's based on the legend of Orpheus, the musician and poet who journeys to the underworld to bring back his dead wife, Eurydice.

NPR: Janacek's 'The Cunning Little Vixen'

Not from an inadvertent glance or a yearning gaze did Orpheus lose Eurydice forever, but from an act of renunciation born of existential despair.

NEWYORKER: The Inconsolable One