Set in the 1870's..survivors of a shipwreck..are saved by the demented creator of "The Natilus".."Captain Nemo"(Robert Ryan)..who makes them newly appointed citizens of his underwater domain"Templemir"..some of the survivors accept the situation..but US Senator"Robert Fraiser"(Chuck Connors),"Mr.Lomax" and two gold thieves"The Bath Brothers:Barnaby and Swallow"have no desire to remain in this underwater place..and they plan to escape.