It’sthedeepestpartofwinter,theexactmidpoint,ChristmasEve–halfwayoutofthedark.AmyandRoryaretrappedonastrickenspacelinerthat’splummetingthroughbanksofthickicyfogtothesurfaceoftheplanetbelow.Onlyonemanhasthepowertosavethem;onlyonemanisinpossessionofamachinethatcanclearthefogandletthemlandsafely.ThatmanisKazranSardick,arichbutlonelyoldmiserwhorulesSardicktownwithasky-mastofiron.TheDoctor’sonlychanceofrescuingtheship’s4,000passengersistosaveKazran’ssoulandshowhimthatlifeisworthliving.Forthisheneedstogoback,wayback,towhenKazranwasaboywithalifefullofpromise.ButcantheDoctorputasonginKazran’sheartandloveinhislife,intimeforChristmas?Canhebringhimoutofthedark?