The Purple Cloud, The Lord of the Sea (both 1901), and The Last Miracle (1906) is a trilogy of science fiction; and at least the first two are considered early masterpieces in the genre. The Purple Cloud is widely hailed as a masterpiece of science fiction and one of the best last man novels ever written.
Adam adventures to the North Pole; on returning he realizes the entire population of the world has been destroyed by a cloud of cyanogen; he tours with world as master of all he sees, reveling and destroying as he will.