WhenamysteriousanddangerouswhirlpoolphenomenonappearsinthetropicsoftheAtlanticOcean,BelkaandStrelka,thefirstastronautsontheirwaybackfromamissiontoSaturn,aresenttoinvestigate.Astheyventuredownintotheswirlingoceandepths,theydiscoveramysteriousUFOattemptingtostea...