The sixth in a popular series brings an end to witchy Mrs. Tuggle after a yearlong struggle by Lynn Morley and her friend Mouse. Although Mrs. Tuggle apparently died in a fire months ago, continued manifestations of her evil support the girls' conviction that she was a witch. As they begin seventh grade, her house is reconstructed; its new occupant, Greta Gullone, alleges that she's Mrs. Tuggle's sister. Terrified, Lynn thinks, "What if...amid smoke and flames, she had bodily transfigured herself into something else...and now she was back, masquerading aa her own sister." Mounting evidence supports this idea as Mrs. Gullone's activities increase and adults become involved; her power is broken when Mr. Morley accidentally injures her rabbit familiar. She sickens in sympathy; joining together, the families overcome her evil with good in a scary, highly satisfactory resolution. A bravura performance by Lynn, strong and steady throughout the ordeal, and by Naylor, who maintains the taut pace right to the end. This last story contains a complex weave of flashbacks to the earlier books as well as new horrors: gratifying for old fans, an irresistible lure for new ones. (Fiction. 8-12)