Shortlybeforeheistowed,millionaireJohnWillisisvisitedbyDr.HarryS.Blair,apsychiatristwhoinformshimthatyearsbeforehewasmarriedtoNancy,John'swife-to-be,andwarnshimthatsheismentallyunbalanced.
Blairthenrelatesthefollowingstory:AfterawhirlwindromanceinFlorida,BlairmarriesNancyandstartsapsychiatricpracticeinNewYork.Oneday,artistNormanClydecomestohisofficeandtellshimthataninnocentmanisabouttobeexecutedinSingSingPrisonandthatNancyisthecauseofhisunjustincarceration.AdistraughtClydethenexplainshimselftoacuriousBlair:
Threeyearsbefore,ClydemeetsNancy,whosemaidennamewasMonks,whensheenrollsinhisartclass.ThemoodyClydesoonfallsinlovewithNancy'shonestcharmandbeauty.Nancy,asecretary,introducesClydetoherboss,millionaireAndrewBonner,andpersuadesBonnertoshowcaseClyde'spaintingsatoneofhisprivateshowings.ToNancy'sdelight,Clyde'spainting,adepictionofthetragicfigureCassandraforwhichshemodeled,winsfirstprizeattheshowing.Theeveningisperfectuntilanexpensivebraceletisstolenfromaguest,andClydelaterfindsitinNancy'spurse.AfterClydeconfrontsaconfusedNancyaboutthetheft,sherelatesthefollowingstorytoexplainherbehavior:
Asayounggirl,NancyliveswithherhousekeepermotherinthelavishWillishomeandplayswithKaren,theWillises'littledaughter.AlthoughKarenwantstoinviteNancytoherupcomingbirthdayparty,Mrs.Willisrefusestoallowthelower-classNancytoattend.Atruefriend,KarenpromisestogiveNancyoneofthepinsherguestsarereceiving.WhenKarenrealizestherearenoextrapins,however,sheoffersNancythebeautifullocketshehasjustreceivedfromhermother.Nancy'ssubsequentjoyissooncrushedwhenMrs.Willisdemandsthatshereturnthelocket.Later,thelocketisdiscoveredmissing,andNancyisaccusedoftheft.AlthoughNancy'smothersoonfindsthelocketinKaren'sdress,Mrs.WillisrefusestobelieveNancyandforcesherto"confess."
TheadultNancythenadmitstoClydethatthischildhoodhumiliationcausedherunconsciousdesiretostealthebraceletattheparty.AfteraforgivingClydereturnsthebraceletanonymously,heandNancycontinuetheirromanceuntilthenextpartyattheBonners'.SuspectingthattheabsentNancyisspendingtheeveninginBonner'sarms,ClydeleavesthepartytolookforherandseesherexitingMrs.Bonner'sbedroomjustaftertwogunshotsarefired.Bonnerisfoundmurdered,andMrs.Bonner'sdiamondnecklace,stolen.AlthoughNancyandClydearequestioned,valetMyronDexteriseventuallyfoundguiltyandissentencedtodie.Clyde,however,stronglysuspectsNancy,butsheangrilymaintainsherinnocenceandleavesforFlorida.
Backinhisoffice,BlairdefendsNancytoClydebutinviteshimtohishousethatevening.Whenconfronted,NancydenieseverythingandtellsBlairthatClydeismerelyjealous.Thenextday,Dexterisexecuted,andaguilt-riddenClydejumpsfromBlair'sofficewindowtohisdeath.
Toavoidscandal,BlairandNancymovetoEngland,andafterWorldWarIIbreaksout,Blairvolunteershismedicalservices,whileNancybecomesanambulancedriver.ExpressingconcernoverBlair'shealth,NancyinsiststhattheytakeavacationatLordandLadyWyndham'smanorhouse.Justastheyareleaving,BlairlearnsthatoneofLadyWyndham'svaluablejewelshasbeenstolen.BlairsuspectsNancybutisunabletoproveanythinguntilabombdestroystheirflatandrevealshercacheofstolenjewels.
Althoughconfronteddirectly,NancycontinuestodenyanyguiltanddivorcesBlairafterhesuffersanervousbreakdown.BackinJohn'sstudy,Blair,likeClydebeforehim,triestoconvinceJohntoabandonNancy,whonowusesthenamePatton.John,however,believesNancywhenshetellshimthatBlairisstillsufferingfromhisbreakdown.
Momentsbeforetheweddingistostart,Nancy'sfuturemother-in-law,theunsuspectingMrs.Willis,givesherthesamelocketthatsheoncetookaway,andtellsherthatitisapreciousfamilyheirloom.ThelocketcausesNancytobeovercomewithguilt,andshecollapsesatthealtarinhysterics.AsNancyislatertakenawaytoaninstitution,JohnsadlyrealizesthetruthofBlair'sstory,butdeterminestoseeNancythroughhercrisis.
