Set in 1865 during the American Civil War, Capt. Harding (Michael Craig) and two Union PoWs, a war reporter and a Confederate deserter escape the siege of Richmond in a huge observation balloon. Pounded by a violent storm, just as the balloon tears they land on an un-chartered South Sea island somewhere near New Zealand. The fugitives soon discover that this is no ordinary desert isle after a bruising encounter with a giant crab. They are soon joined by a pair of shipwrecked British ladies (Joan Greenwood and Beth Rogan) who were en-route to Marseille.
The castaways find further evidence of outsized creatures in the form of an enormous bird and huge bees but when they discover the bird had been shot and a treasure-chest of essentials are washed-up on the beach they can’t shake the feeling they’re not alone and being watched. Sure enough, it turns out that the island is the residence of Captain Nemo (Herbert Lom), skipper of the now un-seaworthy submarine Nautilus. Having failed to end all wars by blasting battleships out of the sea, Nemo is now experimenting with new means of ending world starvation: hence the outsized crabs and birds that the castaways have tackled. Nemo intends to spread his breakthrough discoveries throughout the world but before he and the castaways can set sail on a sunken pirate ship that Nemo had helped to float there’s the small matter of a simmering island volcano. —Britmovie.co.uk