The sinister Emperor Moth has captured Mimi, a lovely butterfly with a past. Meanwhile, Leon Leafwing, in love with Mimi and desperate to rescue her, enlists the aid of Spider Kane, the Sherlock Holmes of the bug world, who leads a perilous rescue mission to the Emperor's rotting palace deep in the Dark Swamp. The kidnapping and rescue all prove to be an elaborate charade, designed to test Leon's mettle and determine whether he's brave and dependable enough to join the Order of the MOTH, an elite band devoted to solving mysteries and fighting injustice. Using skills honed in her realistic novels (last One Home, 1987), Osborne differentiates a sizable cast of creepy-crawly characters and will keep readers guessing; the clothed creatures in Chess's numerous b&w illustrations have her amusing trademark moon faces with prominent noses and round white eyes. A quality book that may need booktalking to find its audience--many children young enough to like a story in which all the characters are bugs will not be able to read it. Adults who read the book aloud will be rewarded with a novel sendup of the Genteel Amateur Sleuth genre. A sequel is in the works.