. ▁ ▁Plot ▁summary ▁▁ ▁The ▁Sol ar ▁System ▁has ▁div ed ▁into ▁a ▁bel t ▁of ▁cos mic ▁dust ; ▁Britain ' s ▁climate ▁has ▁changed ▁from ▁temper ate ▁to ▁ar ctic . ▁ ▁Professor ▁Mill ward ▁has ▁stayed ▁with ▁his ▁books , ▁when ▁the ▁country ▁was ▁abandoned ▁more ▁than ▁twenty ▁years ▁ago , ▁and ▁lost ▁track ▁of ▁the ▁others ' ▁attempts ▁to ▁colon ize ▁the ▁rapidly ▁transform ing ▁j ung les ▁and ▁desert s ▁of ▁the ▁south , ▁also ▁via ▁the ▁radio , ▁some ▁years ▁later . ▁He ▁is ▁now ▁shelter ing ▁from ▁the ▁cold ▁in ▁the ▁ed ifice ▁of ▁a ▁London ▁university . ▁Over ▁months , ▁he ▁is ▁ha unted ▁by ▁a ▁myster ious ▁sound ▁from ▁the ▁north , ▁which ▁he ▁attributes ▁to ▁" mount ains ▁on ▁the ▁march ", ▁in ▁his ▁dream s . ▁Ro aming ▁about ▁the ▁snow - bound ▁familiar ▁roads ▁and ▁houses ▁of ▁the ▁city ▁long ▁after ▁the ▁last ▁st ray ▁dogs ▁have ▁disappeared ▁from ▁them , ▁he ▁is ▁surprised ▁by ▁wol ves , ▁rein de er , ▁and ▁polar ▁be ars , ▁and ▁therefore ▁p onders ▁if ▁the ▁ro aring ▁in ▁the ▁north ▁may ▁be ▁caused ▁by ▁an ▁expedition ▁from ▁North ▁America ▁across ▁the ▁fro zen - over ▁Atlantic ▁or ▁by ▁efforts ▁to ▁free ▁the ▁land ▁from ▁ice ▁and ▁snow ▁with ▁atomic ▁bomb s . ▁When ▁he ▁clim bs ▁to ▁his ▁usual ▁look - out , ▁on ▁an ▁especially ▁clear ▁day , ▁he ▁finally ▁detect s ▁the ▁real ▁origin ▁of ▁the ▁northern ▁sound , ▁catch