Best friends Doug and Milo, both 12, along with Doug's worldly cousin Cassandra, 14, discover a fountain of youth; the water halves the age of whomever drinks it, but only for three hours. The boys enjoy shrinking to age six and going trick-or-treating and playing at the mall. Others know about the fountain, however, and will stop at nothing to get control of it. Only occasionally suspenseful, this lightweight story never deals with the real issues raised by shrinking, and will strike anyone who has seen the movie Big, or read Mary Rodgers's Freaky Friday (1972) and Summer Switch (1982) as lacking in originality. The writing is unclear and sometimes hard to follow, while the bad guys move abruptly from blandly manipulative to seriously evil. Goldman (Getting Lincoln's Goat, 1995, etc.) offers a fast read, but not a very interesting one.