 Science professor John Butler and his family - wife Kim, teenage daughter Katie, young son Greg (the siblings always go barefoot), and dog Digger - are on a rafting trip along the Amazon River when their raft hits a rock and capsizes.They are swept through a cavern and caught in a whirlpool; upon resurfacing, they find themselves in a mysterious realm where humans coexist with various prehistoric creatures, including dinosaurs.The Butlers meet and befriend a clan of Neanderthals led by