Barbara Carey travels to Italy to visit her blind sister Marianne but upon arrival finds that her sister's been missing for weeks. She soon becomes involved with the murder of her sister's boyfriend, a mysterious diver, and another missing blind girl.

Barbara feigns blindness in order to attract the attention of millionaire David Malcolm, whom she suspects is the serial killer targeting blind women after someone makes the remaining victim commit suicide by playing seagull noises.

David invites Barbara to stay at his private island where he lives with his controlling cousin and sinister manservant.

Frederick, David's concealed disfigured son, falls in love with Barbara just as Martin, her boyfriend, comes to Seagull Island looking for her.

Barbara uncovers David's darkest secret. Will Martin and the police be too late to save her and the other inhabitants of Seagull Island?