Stephen Forsyth as John Harrington

Dagmar Lassander as Helen Wood

Laura Betti as Mildred Harrington

Jesús Puente as Inspector Russell (as Jesus Puente)

Femi Benussi as Alice Norton

Antonia Mas as Louise

Luciano Pigozzi as Vences (as Alan Collin)

Gérard Tichy as Dr. Kalleway (as Gerard Tichy)

Verónica Llimerá as Betsy Wester (as Veronica Llimera)

Pasquale Fortunato as John Harrington as a Boy (as Fortunato Pascuale)

Ignasi Abadal as Jimmy Kane (as José Ignacio Abadaz)

Silvia Lienas as Vicky

Montserrat Riba Vidal as Rosy Miller (as Monserrat Riba)

Susy Andersen as Sdenka (archive footage) (uncredited)

Guido Barlocci as Unknown (uncredited)

Bruno Boschetti as Policeman (uncredited)

Elina De Witt as Model (uncredited)

Rika Dialina as Maria (archive footage) (uncredited)

Boris Karloff as Gorca (archive footage)

Glauco Onorato as Giorgio (archive footage) (uncredited)