TheDoctorisanobserverandUNITareprovidingsecuritycoveratanexperimentaldrillingprojectdesignedtopenetratetheEarth'scrustandreleaseapreviously-untappedsourceofenergy,namedStahlman'sGasafteritsdiscoverer.ProfessorStahlmandi*issestheconcernsoftheproject'sExecutiveDirectorSirKeithGoldandexceedsallsafetymarginsinordertoexpeditethework.Soonhoweverthedrillheadstartstoleakanoilygreenliquidthattransformsthosewhotouchitintoviciousprimevalcreatureswithacr*ingforheat.TheDoctorisaccidentallytransportedbythepartially-repairedTARDIScontrolconsoleintoaparalleluniversewhereEnglandisruledbyamilitarydictatorship.Thedrillingprojectisatamorea*ancedstagehereand,thwartedbyhisfriends'ruthlessalteregos,heisunabletopreventthepenetrationoftheEarth'scrust,whichultimatelycausestheplanet'sdestruction.Escapingbacktohisownuniverse,wherethedrillingisstillinprogress,theDoctortriestowarnofimpendingdisaster.Atfirstheisdi*elieved,buthiswordsareborneoutwhenthepower-crazedStahlmanishimselftransformedintooneofthehideousprimordialcreatures.TheDoctor,aidedbyconsultantGregSutton,killsStahlmanwithice-coldblastsfromfireextinguishers.Heisfinallyabletoshutdownthedrillingwithonlymomentstospare.