On a zoology expedition up the Amazon, Professor Challenger has made an inexplicable discovery. Back in London, his claims are ridiculed throughout the professional community. Reluctantly, he recounts to Journalist Edward Malone, ""Curupuri is the spirit of the woods, something terrible, something malevolent, something to be avoided. None can describe its shape or nature, but it is a word of terror along the Amazon. Something terrible lay that way. It was my business to find out what it was.""