▁air port ▁by ▁an ▁un mann ed , ▁computer - control led ▁Douglas ▁C - 4 7 ▁aircraft ▁with ▁no ▁windows . ▁Land ing ▁in ▁a ▁remote ▁area ▁of ▁Georgia , ▁he ▁finds ▁an ▁international ▁group ▁of ▁top ▁scient ists ▁already ▁present , ▁including ▁an ▁old ▁fl ame , ▁Dr . ▁Ruth ▁Adams . ▁Cal ▁is ▁confused ▁by ▁Ruth ' s ▁failure ▁to ▁recognize ▁him ▁and ▁susp icious ▁of ▁Ex eter , ▁his ▁assistant ▁Bra ck ▁and ▁other ▁odd - looking ▁men ▁leading ▁the ▁project . ▁ ▁Cal ▁and ▁Ruth ▁fle e ▁with ▁a ▁third ▁scient ist , ▁Steve ▁Carl son , ▁but ▁their ▁car ▁is ▁attacked ▁and ▁Carl son ▁is ▁killed . ▁When ▁they ▁take ▁off ▁in ▁a ▁St inson ▁ 1 0 8 ▁light ▁aircraft , ▁Cal ▁and ▁Ruth ▁watch ▁as ▁the ▁facility ▁and ▁all ▁its ▁inhabitants ▁are ▁inc iner ated . ▁Their ▁aircraft ▁is ▁then ▁drawn ▁up ▁by ▁a ▁bright ▁beam ▁into ▁a ▁flying ▁sau cer . ▁Ex eter ▁explains ▁that ▁he ▁and ▁his ▁men ▁are ▁from ▁the ▁planet ▁Metal una ▁and ▁are ▁locked ▁in ▁a ▁war ▁with ▁the ▁Zag ons . ▁They ▁defend ▁against ▁the ▁Zag ons ▁with ▁an ▁energy ▁field , ▁but ▁are ▁running ▁out ▁of ▁u ran ium ▁to ▁keep ▁it ▁running . ▁They ▁en list ed ▁the ▁humans ▁in ▁an ▁effort ▁to ▁transm ute ▁lead ▁to ▁u ran ium , ▁but ▁time ▁has ▁run ▁out . ▁Ex eter ▁takes ▁the ▁Earth lings ▁back ▁to ▁his ▁world , ▁se aling ▁them ▁in ▁protect ive ▁tub es ▁to