StephenArrowsmith(PaulMuller),ascientistexperimentingwiththepossibilityofregeneratingbloodthroughelectricityhashishomeandlaboratoryinthecastleownedbyhiswifeMuriel(BarbaraSteele).ArrowsmithfindsherlaterhavingsexwithagardeneranddisfigureshimwithahotpokerandburnsMuriel'sfacewithacidbeforeelectrocutingbothofthem.ArrowsmithhidestheirheartsinanurnandthenusestheirbloodtorejuvenatetheagedservantSolange(HelgaLiné)eee
　　Later,ArrowsmithrealizesthatheisnotMuriel'sheir,butthattheestatehasbeenwilledtohersisterJenny(BarbaraSteele).Jennyismentallyunstable,andArrowsmithmarriesher,laterplanningtohaveSolangedrivehertothebrinkofsanity.JennybeginshavingnightmareswhichincludethesoundofbeatingheartsandMuriel'svoiceurginghertomurderStephen.ArrowsmithbringsJennytothedoctorDerekJoyce(MarinoMasé)whoisconvincedthatsupernaturalforcesareatwork.ArrowsmithlatertriestogiveSolangeanotherbloodtransfusion,thedoctorthendiscoversthehiddenheartsofMurielandthegardener.ThetworeturnasghostswithMurielburningStephenalivewhileDavidreducesSolangetoaskeletonbysuckingherblood.ThedoctorandJennyleavethecastleandconsignthetwofoundheartstoafire.