Merilla, a mermaid, must save four humans to earn a soul and human body. She falls for Prince Hero but lets him unite with his true love after saving princess Leanda from villain Boreas, sacrificing her own love but gaining humanity.

Merilla (Annette Kellerman), Queen of the Seas, finds a book among the wreckage at the bottom of the sea, that contains a prophecy that she shall save four human beings and then receive a human body of her own and an immortal soul. King Boreas (Walter Law), Master of the Storm, wrecks many ships and sends sea sirens to drag the victims to a certain death. Merilla saves the predicted number of lives and the fourth proves to be Prince Hero (Hugh Thompson), who is on his way to meet his betrothed, Princess Leanda (Mildred Keats). Merilla and the Prince fall in love with each other, but Ariela (Beth Irvine) tells them they must be unselfish and the Prince goes on to meet with Princess Leandra, who is really in love with one of her courtiers, Clovis (Fred Drucker). Boreas captures the Princess and puts her in a dungeon. Merilla has been rewarded with a human body and such a beautiful soul that she vows to rescue the Princess even though it means the loss of the Prince to her. She goes to the dungeon, encourages the Princess and walks out on a spider thread to warn the Prince of the great danger to the Princess. The Prince and his Knights come in time to save the Princess from a horrible fate. The Princess confesses her love for Clovis and the two couples are united.—Les Adams <[email protected]>