After a young man is killed in an unexplored subterranean cavern and his girlfriend driven mad by something she saw there, a track found at the scene cannot be identified with any known animal and thus a scientific expedition is launched to find out just what it is that is living there.
Profesor Díaz
Dr. Pena
Hilda Ramírez
Jaime Rocha
Laura Ponce
Dr. Manuel Ríos
Julia
Apolinar
Novio de Julia
Gerente de gruta (uncredited)
Padre de Julia (uncredited)
Turista (uncredited)
Psiquiatra (uncredited)
