Dirección: León Klimovsky
El doctor Jekyll aplica una extraña substancia química sobre el cuerpo de Waldemar, que padece de licantropía, es decir, se transforma en hombre lobo. Como consecuencia de este experimento la personalidad de Waldemar se "desdobla y surge la figura maligna y lujuriosa de Mister Hyde, su alter ego, el cual comete toda clase de atrocidades llegando a asesinar al propio doctor Jekyll.
Paul Naschy
Waldemar Daninsky / Wolfman / Mr. Hyde
Shirley Corrigan
Justine
Jack Taylor
Dr. Henry Jekyll
Mirta Miller
Sandra
José Marco
Imre Kosta
Luis Induni
Otvos
Barta Barri
Gyogyo, the inn-keeper
Luis Gaspar
Thurko, Otvos's thug
Elsa Zabala
Uswika Bathory
Lucy Tiller
Whore
Montserrat Julió
Agatha (uncredited)
Marisol Delgado
Nurse / Victim (uncredited)
María Luisa Tovar
Streetwalker / Victim (uncredited)
Heinrich Starhemberg
Party Guest (uncredited)
Jorge Vico
Adolfo Thous
(as Adolfo Tohus)
Simón Ramírez Fernández
Waldemar Daninsky (voice) (uncredited)
Paul Naschy
Waldemar Daninsky / Wolfman / Mr. Hyde
Shirley Corrigan
Justine
Jack Taylor
Dr. Henry Jekyll
Mirta Miller
Sandra
José Marco
Imre Kosta
Luis Induni
Otvos
Barta Barri
Gyogyo, the inn-keeper
Luis Gaspar
Thurko, Otvos's thug
Elsa Zabala
Uswika Bathory
Lucy Tiller
Whore
Montserrat Julió
Agatha (uncredited)
Marisol Delgado
Nurse / Victim (uncredited)
María Luisa Tovar
Streetwalker / Victim (uncredited)
Heinrich Starhemberg
Party Guest (uncredited)
Jorge Vico
Adolfo Thous
(as Adolfo Tohus)
Simón Ramírez Fernández
Waldemar Daninsky (voice) (uncredited)
Paul Naschy
Waldemar Daninsky / Wolfman / Mr. Hyde
Shirley Corrigan
Justine
Jack Taylor
Dr. Henry Jekyll
Mirta Miller
Sandra
José Marco
Imre Kosta
Luis Induni
Otvos
Barta Barri
Gyogyo, the inn-keeper
Luis Gaspar
Thurko, Otvos's thug
Elsa Zabala
Uswika Bathory
Lucy Tiller
Whore
Montserrat Julió
Agatha (uncredited)
Marisol Delgado
Nurse / Victim (uncredited)
María Luisa Tovar
Streetwalker / Victim (uncredited)
Heinrich Starhemberg
Party Guest (uncredited)
Jorge Vico
Adolfo Thous
(as Adolfo Tohus)
Simón Ramírez Fernández
Waldemar Daninsky (voice) (uncredited)