Milton P. Greene is having a terrible summer. After a public embarrassment, his parents send him to a remote island to stay with his eccentric Uncle Evan. Milton expects boredom, but the island, called Everleaf, is a vibrant, magical wilderness filled with glowing plants and mysterious creatures. Teaming up with a local girl named Fig, Milton embarks on a quest to find a legendary bird and save the island from a strange, creeping blight, discovering his own courage along the way.