The Devil's Partner (1961) – Charles R. Rondeau.

Spooky Theremins and vintage occult horror go together sweeter than good malt whiskey and ice-cold beer, and Rondeau's low budget, yet highly entertaining, Theremin-tastic Faustian shocker is some potently distilled Drive-In deviltry. For a B-chiller produced on such modest means, The Devil's Partner has aged remarkably well, remaining an atmospheric, altogether watchable Black Magic horror gem. Ostracized octogenarian (Ed Nelson) dies in a occulted manner, and not long after, his handsome, boy-next-door nephew (Ed Nelson) arrives, he cosily insinuates himself into this dust-bowl backwater, proceeding to play the good guy card with a little too much zeal. Not unlike a feature-length episode of The Night Gallery, or Boris Karloff's The Veil, The Devil's Partner succeeds due to an engaging text, credible performances, considered film-making, a smattering of small town folksy charm, and a genuinely thrilling final act. As a long-time fan of Ed Nelson, I can state with only a modicum of fanboy hyperbole that his darkly charismatic, devilishly duplicitous antagonist is a palpable (five pointed)star-maker.