AmericanpsychologistJohnHoldenarrivesinLondontoparticipateinasymposiumaimingtoexposewitchcraftanddevilworshipasafraud、withattentioncenteredonacultrunbyaJulianKarswell.Debarkinghisplane Holdenlearnsthatthesymposiumleader、HenryHarrington hassuddenlydiedandheisnowincharge.WhatonlytheaudienceknowsisthatHarringtonwasclearlykilledbyademon, apparentlysummonedbyKarswelltoavengehispersecution.DespiteboththreateningandcajolingbehaviorbyKarswell, Holdendeterminestoproceed thoughtheonlycultmemberwillingtotalkabouthisexperiencesisinaprisonpsychiatricward catatonicafterallegedlykillingyetanothercultmember.However,哈林顿'sniece,乔安娜,相信,basedonheruncle相差不大,thatKarswellmayindeedhavesomesatanicpowersderivedfromanancienttomeinanobscurelanguagewhichhehasbeenabletotranslate, andattemptstowarntheskepticHolden.Karswell 'smotheralsoattemptstowarnHoldenoff.However, thethingwhichbeginstomostgettoHoldenaretheoccasional, butmounting sensoryandmentaldisturbanceshebeginsexperiencingafteranencounterwithKars嗯,andthediscoverythat、duringthisencounter KarswellsecretlyslippedaslipofparchmentwithacurseinrunicsymbolsonitintoHolden 'sbelongings, aparchmentidenticaltooneHarringtonrecordedhavinghadpassedtohiminasimilarmannershortlybeforehisdeath…[N.B.HoldenatnopointstaysattheKarswellestate]。