Phantastes tells of the adventures of a young man named Anodos (which means Pathless in Greek). On his 21st birthday, just after the death of his father, Anodos opens a desk with a key which has been given to him by his father and in it he discovers his late grandmother, who has been transformed into a fairy. The fairy reveals a fairy land of magic and wonder: the walls of his study, made of wood, literally transform into an enchanted wood, and he is transported into fairy land.
In this enchanted kingdom, Anodos has many adventures. He encounters both beauty and danger; and battles evil creatures. In the climax of the book, Anodos comes across an temple dedicated to evil, but disguised as good. Seeing through the travesty, he attacks the grotesque idol of rotting wood, but he is killed by its evil worshippers.
After his death, Anodos floats peacefully over the fairy land and having died nobly, is able to find peace and gain perspective. He awakens back in the real world, alive. Or is he. He is told that he has been gone for 21 days, but to him it felt that he had been in fairy land for 21 years.