Devil Doll (1964)

American investigative journalist Mark English does not much like his first London-based assignment: to do an expose of The Great Vorelli, whose shows demonstrating his skills as a hypnotist and ventriloquist have been selling out. Mark plans on using his girlfriend Marianne Horn, from one of the wealthiest families in England, to assist in his investigation in volunteering when Vorelli asks for a assistant from the audience so that she can get up close and personal in seeing what behind the scenes trickery is involved. In attending one of his shows, Mark and Marianne will discover the stage personae of the ventriloquism portion of the show with Vorelli's dummy named Hugo are as master and subservient, Vorelli not only using the fashionable technique employed by other ventriloquists of having Hugo speak when Vorelli's own mouth is doing other things, but Hugo being self-mobile, including walking across the stage on his own. Mark wants to get as close to Hugo as possible, the dummy to which Vorelli restricts access. In discovering who Marianne is following her appearance on stage, Vorelli has his own plans for her, namely for her to become the next Hugo.