TheTARDISlandsinLondononChristmasEve,1851andalmostimmediatelytheDoctorhearshisnamebeingcalled.WhenhemeetsthewomanshoutingforhimshefailstorecognisehimandcontinuescallinguntilanothermanarrivesandclaimstobetheDoctorandacknowledgesthewoman,Rosita,ashiscompanion.TheDoctorthenattemptstohelpthenewcomerlassoaman-sizedog-likecreaturewhichhasacyber-mask,butitdragsthemboththroughtheupperfloorofawarehouseuntilRositacutstherope,savingthembothfromplungingthroughahighwindow.Thenewcomerexplainshehaslosthismemory,andtheDoctorassumesheisalaterincarnation,andfollowshimtothehouseofamurderedvicar,wherethenewDoctorsaysheisinvestigatingthemurderofthevicarandateachercalledJacksonLake,andthathismemorywaswipedwhenhewasattackedbytheCybermen.AtthehousetheDoctorfindsprimitivememorydevicescalledinfostampsandsaystheyhavebeenusedbytheCybermenbecauseofthelackoftechnologyin19thcenturyLondon.TwoCybermenattacktheDoctors,butaredestroyedwhenthenewDoctorsetsoffafeedbackloopinoneoftheinfostamps,somethinghesaidwasthecauseofhismemoryloss.ThenewDoctortakestheDoctorbacktohisbase,inthestablesofanInn,andshowshimhisTARDIS,aballoon(TetheredAerialRelease,DesignedInStyle).TheDoctorfindsanotherinfostampinthenewDoctor'sluggage,thisonefilledwithinformationabouthim,andconcludesthatthenewDoctorisreallyJacksonLake,buthismemoryhasbeenover-writtenwithdetailsoftheDoctor'slifebytheinfostamp,whichitselfmayhavebeenstolenfromtheDaleks.Lake'smemorystartstoreturn,andheremembershiswifebeingkilledandhissonbeingtaken.Meanwhile,MercyHartigan,aworkhousematronhasjoinedtheCybermenandhadthemkillthevicarsoallthelocalgentlemenwouldattendhisfuneral;shearriveswiththeCybermentoselectfourofthem(therestarekilled)soshecanhavethechildrenintheirworkhouses(includingLake'sson)asalabourforcefortheCybermen,whoarebuildinga'CyberKing'toruleEarth.TheDoctorisunabletostoptheriseofthe200-foottallCyberKing,whichiscontrolledbyareluctantly-conditionedMissHartigan,butrescuesthechildren.HethenusesLake'sballoonTARDIStogetuptotheCyberKingthrone,whereMissHartiganisheld.Hebreaksherconditioning,andherhumanangerdestroystheCybermen.TheDoctorusestheCybermen'sowntimetraveldevicetodragtheCyberKingbackintotheVoid,savingLondon.Thedangerover,Lake,hismemorynowreturning,hiresRositaasnursemaidforhissonandgetstoseeinsidetherealTARDIS,beforeinsistingthattheDoctorjoinsthemforChristmasdinner.