Shot down over Italy and rescued by the resistance, RAF pilot and composer Richard Wilder (Michael Denison) forms a deep bond with the beautiful Alida (Valentina Cortese), who tells him about the legend of the Glass Mountain. After returning home to England, Richard uses the details from the tale to create an opera with the support of his loving wife, Anne (Dulcie Gray). Unable to forget Alida, however, Richard remains conflicted until the night of the opera's premiere, when fate intervenes.