Some snappy lines, an occasional Insight, and a bit of mystery--but mostly sitcom cutesiness applied to stock juvenile-fiction situations. Angel Wilson makes an inauspicious entrance in Billy Beak's unfriendly town--playing witch, she sortof causes mama's darling Junior Jennings to fall from a tree--and even Billy, intrigued, finds her casual lying hard to take. But he goes along with her hunt for the treasure in the ""haunted"" house she's inhabiting--a hunt really meant to prove to her treasure-hunting (archaeologist) father that he should take her along on his trips and to corral the kids who've been shunning her. This confusion of undeveloped purposes is offset to an extent by sheer verve and nerve--and some fun at the expense of loathsome Mrs. Jennings (for whose bridge-club bash Angel's companion Miss Sally makes melt-in-your-mouth chocolate ants). But the tone wavers and the plot wobbles right up to the final discovery of the treasure-owner's bones in a buried chamber--and the children's rescue thanks to a newly-assertive Junior Jennings. Much ado about many flimsy things.