On the mystic island of Lemuria, the cult of Ubasti seek the Egyptian Princess Nadji to sacrifice so that their goddess Ossana, whose soul resides in Nadji's body, may be resurrected by Black Magic. Nadji is located in the Far East port of Suva, but shielded by the White Magical powers of Frank Chandler, an American raised by Eastern mystics who is also known as Chandu. When Chandu takes a voyage alone, however, the evil Voice of Ubasti is able to magically spirit her to Lemuria, where Black Magic reigns supreme. Chandu sets out in pursuit with his sister Dorothy, niece Betty and nephew Bob; but, shipwrecked on the magic island, Chandu finds his family also held prisoner for sacrifice while he is plunged into an endless maze of caverns beneath the evil temple, where both his mortal and magical strength seem rendered useless.

Chandu consults his crystal ball and sees that Nadji, Princess of Egypt, is in danger. She is about to be sacrificed by the black magic cult of Ubasti. Headed for the magic island of Lemuria, he is shipwrecked , washed ashore and captured. He becomes invisible, escapes and after numerous detours is able to rescue the princess.

In an exclusive Swiss school for young girls, Christa Storm discovers she is going to have a baby, and keeps the secret from everyone but her lover, David Perrin, a young medical student. Having been in the private school most of her life, she can't confide in her father whom she hardly knows and, while he wishes to but can't afford to marry her, David can't get the approval of his father.a