AstheFifteenthDoctor\,playedbyNcutiGatwa\,takesovertheTARDISforhisfirstepicadventurehewillbejoinedbyRubySunday\,playedbyMillieGibson\,asshemakesherdebutastheDoctor’scompanion.TheepisodeseestheDoctorcomeface-to-facewiththemythicalandmysteriousgoblinsashislifecollideswithRubySunday\,playedbyMillieGibson.LittleisknownaboutRubySundayasshewasabandonedonChristmasEveasababy.Nowlivingwithhermum\,Carlaandgrandmother\,CherryherworldisabouttobeturnedupsidewhensheencounterstheDoctorandthetwosetoffontheirfirstadventuretogether