The return of The Mouse and the Motorcycle is a departure--from the wide-open corridors of Mountain View Inn to a cage that's also a vantage point in a typical summer camp; but tipping the balance from fantasy to personality doesn't throw freedom rider Ralph. At least not for long. Caught in a generation gap between his timid, crumb-scrounging elders and a horde of little cousins clamoring to ride his shiny red motorcycle, he takes off--speeded by the new force of gravity--for Happy Acres Camp. But watchdog Sam and smug Catso have other ideas, and Ralph's not sorry when new-camper Garf's butterfly net makes him a permanent exhibit in the craft cabin (though the girls' itsy-bitsy, teeny-tiny squeals are a little hard to take). Spinning full circle on his exercise wheel is "as dangerous and exciting as riding a motorcycle" until golden (his emphasis) hamster Chum grumpily reminds him that he's not going anywhere. Then Ralph pins his hopes on Garf, a boy who might understand that Pb-pb-b-b-b-b is the way to make a toy motorcycle go. in the wacky, camp-wise, anything-but-mousie wind-up, he turns the tables on Catso, clears loner Garf of the theft of a watch, and earns his return. . . to the now-valued vistas of Mountain View Inn. The irresistible drawings--of Ralph bent over the breakaway bike, of Catso toying with him to impress his offspring, of Ralph curled up in a Dacron sleeping bag--attest to the rightness, and the sadness, of Mrs. Cleary's dedication (To Louis Darling, 1916-1970). Happily, Ralph will be tearing along in his ping-pong ball crash helmet for a long time, on the elusive trail of peanut-butter-and-jelly sandwiches and boys who go Pb-pb-b-b-b.