Nightmare!

After the 'Lusitania' ship is torpedoed, a man from New York wakes up to find himself in the ocean off an uncharted island. On the magical South Pacific Island, he encounters a brutal wilderness, where plants can eat men and spiders are as big as dining room tables. Before he knows it, he is caught in a dangerous rivalry between two Russian brothers who will do anything to find the philosopher's stone. A tale of mystery, suspense, and endless adventures, "Nightmare!" explores the horrors of the natural world set against the even more gruesome horrors found in the human soul. Francis Stevens is the pseudonym of Gertrude Barrows Bennett (1884-1948), who was a pioneering author of fantasy and science fiction.
Her works explore lost worlds, dystopian societies, and apocalyptic scenarios. If you read H. P. Lovecraft, you'll love Francis Stevens who has been called 'the woman who invented dark fantasy'.