A light mystery, sequel to Mystery of the Night Raiders. Brian, an eighth-grade swimmer and Sherlock Holmes enthusiast, befriends new kid Ralph, a gangly, socially inept joker with a problem of premature hairiness. When their Central Park apartment building yields such clues as pigeon carcasses, gray hair on the elevator buttons, and eerie midnight howling, Brian summons his old friends and fellow monster-hunters Darcy and Numbles--who suggest that a werewolf is the culprit. Is it the lycanthrope Mareck, the evil teen-ager living on the roof--or is it, possibly, poor hirsute Ralph, who lately has taken to growling at people? Unfortunately, there is a tendency toward cuteness here: the chapter entitled ""The Second Body,"" for instance, refers to a pigeon, not a person; and although there are red herrings, Brian does not really engage in deductive reasoning like his hero--rather, he is in the right place at the right time. Meanwhile, Darcy and Numbles, mostly out of town, contribute little to the investigation but make it back in time to help enact a brave rescue. Swimmers will enjoy the authentic swim team details and the splashy finale.