The kids in 207 ""were the worst-behaved class in the whole school,"" even during story hour--a deadly sin. After a surfeit of spitballs, their sweet and permissive teacher, Miss Nelson, reappears disguised as Miss Viola Swamp, and loads them down with homework, forces them to behave, and cuts out story time. The vacuous Detective McSmogg is no help with the disappearance, and the children propose a shark attack or a trip to Mars to explain it. . . ""or maybe Miss Nelson's car was carried off by a swarm of angry butterflies."" Miss Nelson ""returns""--minus wig, ugly dress, false nose--to find the class remarkably changed. The message is clear, the plot predictable, but there's fun in the telling and Marshall's ""stupid,"" innocent, funny-ugly characters. The broadly comic illustrations are varied--individual portraits, full pages--and filled with details like spitballs stuck on the ceiling. Another slightly twisted and engaging Allard/Marshall collaboration.