After being introduced to the world of opera, a fisherman (Jan Kiepura) falls for a woman (Swarthout) whose guardian is a noted composer (Philip Merivale). They met when the fisherman evaded the police by seeking refuge in the village church. While there, they are each captivated by hearing the other singing Mass. The beautiful woman falls in love with the fisherman with the wonderful voice.

An obsessed scientist conducts profane experiments in evolution, eventually establishing himself as the self-styled demigod to a race of mutated, half-human abominations.