TheTARDISmaterialisesatasecretn*albaseoffthecoastofNorthumberlandtowardtheendoftheSecondWorldWar.DrJudson,ascientistthere,hascreatedtheUltimaMachine,anearlycomputerdesignedtobreakGermancodes.Thebase'sCommanderMillingtonplanstoletaRussiancommandounitledbyCaptainSorinstealtheMachine'score,whichheha*ooby-trappedwithdeadlytoxin.JudsonusestheMachinetotranslatesomeancientrunesfromthecryptofthenearbyStJudeschurchandthisleadstothereleaseofFenric,anevilentityfromthedawnoftimewhomtheDoctortrappedseventeencenturiesearlierinaChineseflaskbydefeatingitatchess.TheflaskwaslaterstolenandburiedatthechurchbyVikings.ThebaseandchurchareattackedbyHaemovores.Thesearehumanswhoh*ebeentransformedintohideousvampiriccreature*ytheAncientHaemovore-thelastsurvivorofapollution-r*agedfutureEarth,whoha*eenbroughtbackintimebyFenric.FenrictakesoverJudson'*odytochallengetheDoctortoarematchatchess,andAceunwittinglyhelpsittowin.Fenric,nowinSorin'*ody,revealsthatAce,Judson,Millington,SorinandWainwright,thevicarofStJudes,areall'WolvesofFenric'-pawnsinit*attleagainsttheDoctor.ItnowplanstoreleasethedeadlytoxinbuttheDoctorsucceedsinturningtheAncientHaemovoreagainstitanditshostbodyiskilledbythegas.ThebabydaughterofayoungwomanwhomAcehelpedtoescapefromtheHaemovoresisrevealedtobeherfuturemother.